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2013
2014
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YE
AR
S
DO
ING
EDITION
OU
RB
EST
, SO
SCIENCE
SCIENCE
Genetics
POWER GUIDE
EDITOR
ALPACA-IN-CHIEF
Josephine Richstad
Daniel Berdichevsky
®
the World
Scholar’s Cup®
YO
U
CA
N
DO
YO
UR
S
`s
SCIENCE
®
POWER GUIDE
I.
AUTHOR’S NOTE………………………………………………………… 2
II.
INTRODUCTION…………………………………………………………. 3
III. CELLULAR REPRODUCTION………………………………………… 4
IV. THE PATTERN OF INHERITANCE…………………………………. 29
V.
MOLECULAR GENETICS………………………………………………. 45
VI. CONCLUSION……………………………………………………………… 69
VII. POWER LISTS……………………………………………………………… 70
VIII. PRACTICE TEST ANALYSIS………………………………………….. 139
IX. ABOUT THE AUTHOR………………………………………………….. 141
X.
ABOUT THE EDITOR…………………………………………………..... 142
BY
EDITED BY
ERIC YANG
JOSEPHINE RICHSTAD
THE COLONY HIGH SCHOOL
PHD UCLA - BA COLUMBIA UNIVERSITY
TO THE TCHS NINE THAT COULD
© 2013 DemiDec. DemiDec, The World Scholar’s Cup, Power Guide, and Cram Kit are registered trademarks of the DemiDec Corporation.
Academic Decathlon and USAD are registered trademarks of the United States Academic Decathlon Association.
.
Science Power Guide | 2
AUTHOR’S NOTE
Welcome, fellow Decathletes and future geneticists! By opening this Science Power Guide, you have ventured
on a journey that will cover two fascinating centuries of scientific discovery in the field of genetics, filled with
twists, turns, and the occasional dead end.
I’m Eric Yang, resident science nerd and Honors Decathlete at The Colony High School. Ever since I was a
toddler, genetics has captured my curiosity1. I’ve always been amazed that the diversity of Earth’s 8.7 million
species results from such tiny differences in DNA from one to the next. I hope this Power Guide can help
you learn more about why those differences make the difference that they do.
Throughout the Power Guide, I will be bolding key people, processes, structures, and other important terms.
All of the terms USAD bolds in the Resource Guide will be bolded here as well. A comprehensive list of these
bolded terms can be found in the Power Lists, at the end of the Power Guide. When USAD mentions a
concept in passing without explaining it fully, I will add context and background through footnotes. This
information will not be tested at competition, but will improve your understanding of the material. Footnotes
may also contain supplementary facts, mnemonic devices, or my attempts at genetic comedy. I have signed
those attempts, so feel free to skip those if you’d like to avoid any unnecessary ROFL moments.
Please don’t be daunted by the sheer length of the Power Guide. I’ve rearranged the information in the USAD
Resource Guide to improve learning flow and added plenty of charts, tables, diagrams, and visuals to break
up the endless walls of text that often greet Decathletes when they begin their AcaDec journey.
How to Use This Power Guide
As per USAD, Section I explores the structure of cells and the process of cellular reproduction. Section II
analyzes Mendel’s laws of inheritance and other contributions to the field of genetics, while Section III tackles
genetic research and discoveries in the 20th and 21st centuries.
When reading USAD’s guide, ensure you
understand the techniques used for genetic
analysis (Punnett squares, Hardy-Weinberg
equation, Mendel’s laws of inheritance). This
basic knowledge will help clarify the applications
of genetics found in Section III. I also
recommend using the timelines found in the
back of the Power Guide to study the history of
genetics—it’s crucial to be able to match the
scientists with their discoveries and to remember
the order in which they occur.
Section 3:
Molecular
Genetics
35%
Section 1:
Cellular
Reproduction
30%
Section 2: The
Pattern of
Inheritance
35%
As the days before competition draw near, focus
your studying on Section II. Not only is it the
section most familiar to high school students, but it also accounts for 1/3 of the test while taking up just ¼
of the resource guide. Also be familiar with the terms in the USAD glossary and in the Power Lists at the
back of this guide—they’re a gold mine for test writers.
1
I was also resident science nerd in my family.
Science Power Guide | 3
INTRODUCTION
POWER PREVIEW
POWER NOTES
Gregor Mendel laid the foundations of genetics 150 years ago,
but not until the early 1900s did scientists make major
breakthroughs in our understanding of genes and the
inheritance of traits from generation to generation. Today,
scientists apply genetic knowledge in a wide range of fields,
ranging from cancer treatments to criminal suspect
identification.
 According to the USAD outline, 0
questions should come from the
Introduction.
 0 questions come from the Introduction on
the USAD Science Practice Test
 The Introduction covers pg. 5 of the USAD
Science Resource Guide
Why Genetics?
 A Brief History
 The Austrian monk Gregor Mendel launched the field of genetics
 He sought to understand why purple flowers could produce white offspring
 Few scientists were aware of Mendel’s work until the first decade of the 20th century
 Today, genetics has affected many areas of our society
Cancer and heart disease treatment
Drug production
Expansion of agricultural yields
Criminal suspect identification
Study of evolution
 Section I explains basic cell structures and processes
It covers cellular evolution and the life cycle of a cell
Cellular division is the foundation for more complex concepts, such as the replication of
genetic material
 Section II focuses on Mendelian genetics and its rediscovery around World War I
 Sexually reproducing multicellular species have a wide range of inheritance patterns
 Knowing these patterns can help scientists predict the inheritance of defective genes in
offspring
 Section III discusses the modern synthesis of genetics and evolution
 This section also examines genetics at the molecular level
 Finally, the guide takes a closer look at current frontiers in genetics
 These frontiers include epigenetics and modern applications of genetic information


Science Power Guide | 4
CELLULAR REPRODUCTION
POWER PREVIEW
POWER NOTES
The field of genetics originated in Greek philosophy over two
thousand years ago, but the combination of Gregor Mendel’s
and Charles Darwin’s studies brought it to the forefront of
modern science. In order to understand genetics, we must fully
grasp the complex structure and functions of prokaryotic and
eukaryotic cells, the processes that make up the cell cycle, and
the biological principles of reproduction that are the
cornerstone of Mendelian genetics.
 According to the USAD outline, 15
questions (30%) should come from Section I
 11 questions (22%) come from Section I on
the USAD Science Practice Test
 Section 1 covers pgs. 6 - 29 of the USAD
Science Resource Guide
A Not-So-Brief History of Genetics
 Genetics Before Mendel
 Many scientists and philosophers have speculated about reproduction, embryonic
development, and heredity2
.
Aristotle (384-322
B.C.)
Hippocrates (460-370
B.C.)
Socrates (469-399
B.C.)
Plato (428 - 348 B.C.)
 Aristotle hypothesized that the male parent passes a miniature individual to the female
parent through blood3 transmission4
2
Perhaps teenagers would spend less time on TMZ and more time on cool science experiments if they could all grow devilishly awesome
beards like the Greeks. - Eric
3
That would probably make The Talk less embarrassing for everyone. –Josephine
4
Aristotle isn’t referring to the blood in your arteries, but to semen (which he considered a purified form of blood) and a woman’s
menstrual flow.
Science Power Guide | 5
Once inside the female, the individual grows and
matures in the womb
 Aristotle explained his hypothesis in both the History of
Animals and Generation of Animals
 The idea lasted for over 2,000 years, despite the
invention of the microscope5
 Nicolaas Hartsoeker reinforced the idea with his
drawing of miniature men (homunculus) within a
sperm cell
 Hippocrates developed the theory of pangenesis6
 In Greek, “pangenesis” translates to “whole birth”
 The theory explained why parents and children
had similar traits
 He suggested that human organs came from organ
seedlings called gemmules
 He thought gemmules migrated to the
reproductive organs at sexual maturity
 Organ gemmules from each parent mixed to
form offspring
 Joseph Kolreuter demonstrated the theory of blending
inheritance7 in the 1760s8
 He conducted the first genetic crosses in scientific
history using tobacco plants
 Charles Darwin incorporated blending inheritance
into his theory of evolution

 Mendel and Beyond
 Gregor Mendel radically altered scientists’
understanding of genetics
 In 1847, he entered a monastery in Brno, AustriaHungary
 Brno is located in the present-day Czech
Republic
 He would receive an education while training as a
priest
 Mendel wanted to become a teacher

He had prior experience as a substitute

However, he failed his licensing exam9
 The monastery sent him to the University of Vienna for further education
 He later returned to Brno and embarked on his breeding experiments
5
Microscopes allowed scientists to see the cell and its contents for the first time in history. Unfortunately, the cells that 17th century
scientists Hooke and van Leeuwenhoek studied were noticeably devoid of miniature human individuals.
6
Pangenesis was Charles Darwin’s preferred explanation for the heredity of traits: http://tinyurl.com/mog9m47
7
According to blending inheritance, the range of traits in the parents randomly determined the offspring’s traits. For example, if the
mother was short and the father was tall, the child would have to be shorter than the father and taller than the mother. However,
eventually all the members of a generation would have the same height.
8
USAD does not clearly explain the difference between pangenesis and blending inheritance in the resource guide. After external
research, I’ve come to believe that pangenesis is a “sub-theory” that biologically explains blending inheritance.
9
Twice.
Science Power Guide | 6
While at Brno, Mendel cross-fertilized 30,000 pea plants10 from 1856 to 1864
11
 His experiments led him to develop the three laws of genetics
12
 Mendel published Experiments on Plant Hybridization in 1866 in a local journal
13
 In his paper, he theorized that a “heritable factor” controlled every trait

This “heritable factor” would later be called a gene14
 The scientific community overlooked Mendel’s article during his lifetime
 Mendel’s contemporary Charles Darwin developed his theory of natural selection in the
mid-1850s
 Darwin jointly presented his theory with British naturalist Alfred Russel Wallace at the
Linnean Society of London151617 in 1858
 Wallace studied Asian and Australian animals in the East Indies
 Mendel's work gained new relevance when scientists discovered chromosomes in 1878
 “Chromosome” means “color body” in Greek
 This name arose when scientists found that certain dyes could stain them intensely
 Three European scientists independently developed a method of staining chromosomes
and the nucleus18

Eduard Strasburger (Poland)
Edouard van Beneden (Belgium)
Walther Flemming (Germany)

They sought to understand the process of cell division

Walther Flemming termed this process mitosis

This word came from a Greek word meaning “thread”
 Genetic Discoveries of the Early 20th Century
 In 1900, three scientists independently confirmed Mendel’s work
10
Apparently he began with animal breeding, but his superiors thought that was too racy for a monastery. –Josephine
These are the law of segregation, law of independent assortment, and law of dominance. USAD explains these laws in Section II of the
Resource Guide, so I will do the same.
12
Specifically, the Proceedings of the Natural History Society of Brno. They had wild parties.
13
Mendel himself called this heritable factor an “allele”.
14
Hugo de Vries used the word "pangen" for particles of hereditary in 1889, while Wilhelm Johannsen used "gene" in 1909.
15
USAD mentions on page 7 of the Resource Guide that Darwin presented his ideas “at the prestigious Royal Academy of Science”, also
known as the Royal Society. Darwin was elected a fellow of this society in 1839, but most external sources point to the Linnean Society
of London as the correct target audience.
16
Neither Darwin nor Wallace presented their ideas in person, as Darwin’s infant son had recently died of scarlet fever and Wallace was
travelling in the East Indies. Instead, each wrote a paper detailing their theories that was to be read aloud. Today, they'd deliver their
talks through Skype.
17
In a now–infamous statement, the president of the Linnean Society later wrote that the year 1858 contained no discoveries that would
“revolutionize science”. Oops.
18
Each of these three scientists discovered chromosomes in a different way. For example, while experimenting with cells from the fins
and gills of salamanders, Walther Flemming discovered a basophilic (base-loving) cellular structure that absorbed the basic dyes he
stained them with (thus the name “color body”). He called this structure chromatin.
11
Science Power Guide | 7
Carl Correns
(Germany)
Hugo de Vries
(Netherlands)
Erich von
Tschermak (Austria)
These scientists linked genetics and evolution through studies of hybridized plants
 All three scientists reached the same conclusions as Mendel did
 De Vries first studied the role of mutation in evolution in 1890

De Vries acknowledged Mendel’s legacy when he published his work in 1900
19
 Correns investigated the effect of extra-chromosomal factors on phenotypes

Like Mendel, Correns experimented with pea plants

He confirmed Mendel’s laws of segregation and independent assortment in a
January 1900 paper
20
 Tschermak-Seysenegg confirmed Mendel’s 3:1 phenotype ratio through plant
breeding experiments

He published his work in June 1900

Coincidentally, Tschermak-Seysenegg's grandfather taught Mendel botany at
the University of Vienna
 Walter Sutton (United States) and Theodor Boveri (Germany) observed the segregation of
chromosomes in the nucleus during meiosis21
22
 These two scientists first recognized the role of chromosomes in inheritance
 In 1905, William Bateson and Reginald Punnett discovered linked genes23 and epistasis24
 Bateson previously studied the genetics of sweet peas
 He coined the term “genetics”
25
 In Greek, “genno” means “to give birth”
 He also translated Mendel’s works into English
 In 191026, Nettie Stevens and Edmund Wilson
XX
discovered that human males and females have
(female)
XY (male)
different sex chromosomes
 Females have two X chromosomes
 Males have one X and one Y chromosome
 Sex chromosomes control traits such as color blindness and hemophilia

19
Phenotypes are an organism’s physical traits. They will be explained in further detail in Section II.
Now that’s a mouthful - Eric
21
During segregation, the two alleles responsible for a trait separate during gamete formation. This concept will be explained in more
detail in Section II.
22
This, conveniently enough, is known as the Boveri-Sutton chromosome theorem
23
Linked genes … wait for it … will be explained in further detail later.
24
Epistasis occurs when multiple genes control one trait, but one pair of alleles modifies or hides the effect of the others. Epistasis is
similar to polygenic inheritance, but in polygenic inheritance each gene is expressed equally: http://tinyurl.com/n7ko5oy
25
It also gives us such words as "generate," "general," "genealogy," and "Eugene."
26
USAD states that the sex chromosome was discovered in 1910, but Steven Brush’s article Nettie M. Stevens and the Discovery of Sex
Determination by Chromosomes, published in Isis in 1978, points to 1905 as the correct date.
20
Science Power Guide | 8
Mendel’s law of independent assortment27 does not apply to sex-linked traits
In 1902, Archibald Garrod investigated and described
alkaptonuria, or black urine disease
 The disease results from a faulty amino acid
metabolism enzyme
 The enzyme accumulates in blood and urine

It causes patients' urine to turn brown when
exposed to air

It also damages the heart valves, kidneys, and
cartilage
 Alkaptonuria was the first disease linked to genes
 Garrod called this disease “an inborn error of
metabolism” in a 1908 report
 Genetic diseases such as alkaptonuria are carried
on recessive alleles
Thomas Hunt Morgan was the first geneticist to study
animals
 Mendel had only conducted studies of plants

They bred easily and could be experimentally manipulated

However, the genetics of animals more closely resemble human genetics
28
 Morgan concentrated his efforts on the pattern of eye color inheritance in fruit flies
 He discovered fruit fly eye color was a sex-linked trait
Estella Elinor Carothers presented the first cytological29 evidence of Mendel’s law of
independent assortment
 She observed cell division in grasshopper testis
Geneticist and statistician R.A. Fisher published a 1918 paper uniting evolution and
Mendelian genetics
 Fisher also studied population genetics, sexual selection, and fitness
30
 He is best known today for launching the era of modern evolutionary synthesis
 He worked alongside Sewall Wright and J.B.S. Haldane in this endeavor





R.A. Fisher
(Great Britain)
Founders of
modern
evolutionary
synthesis
Sewall Wright
(United States)
J.B.S. Haldane
(Great Britain)

27
Fisher controversially supported eugenics in the early 1900s
This law states that alleles for different traits are distributed to offspring independently from one another. Mendel’s three laws will be
further explained in Section II.
28
What do you call a Drosophila who likes to drink? A bar fly—Eric
29
Cytology means “the study of cells”, so Carothers discovered the first cellular evidence
30
This was the union of numerous scientific ideas that provided a concrete basis for the theory of evolution.
Science Power Guide | 9
Eugenics grew out of the Social Darwinist31 movement in the late 1800s

Social Darwinists argued that selective breeding could “improve” the genetic
composition of certain populations

They often sought to achieve racial purity and supremacy
Thomas Morgan showed that that environmental factors could alter fruit fly genes
 His experiments undermined eugenicists' strict focus on "nature" rather than
"nurture"
 Most scientists discredited eugenics after World War II

Morgan's experiments played a role

However, it was used as justification for widespread genocide32

Scientists were wary of eugenics'
association with genocide


 The Discovery of Cells
 In order to investigate inheritance, scientists first needed
to understand the fundamental structures of life
 Advanced laboratory instruments and technologies
boosted new biological discoveries in this area
 The microscope has been particularly important
 In the 18th century, Carolus Linnaeus (Carl von Linne33)
first categorized and named living organisms
 He classified all living things into the animal,
vegetable, or mineral kingdoms
34
 He did not include eubacteria or archaebacteria
 Linnaeus is considered the father of modern
taxonomy35
 Today, scientists categorize all 1.8 million species on
Earth into three domains36
Domains of Life
Eukarya
Bacteria
Archaea
 The cell is the fundamental unit of life
The human body alone holds 50 trillion cells
 10 to 20 times more microbes inhabit our bodies

These microbes can be any of over 1,000 different species37
 Robert Hooke first observed the cell in 1665

31
According to Social Darwinism, only the strongest members of human society deserved to live and reproduce. Otherwise, the human
race would slowly degenerate.
32
i.e. the Holocaust
33
Linnaeus changed his last name when the Swedish king Adolf Frederick granted him nobility in 1761.
34
Today, scientists divide life into six kingdoms: Eubacteria, Archaebacteria, Fungi, Protista, Animalia, and Plantae.
35
As mentioned earlier, taxonomy is the scientific discipline concerned with naming and describing species.
36
The domain is the highest taxonomic rank, above the kingdom. All life on Earth can be categorized into one of the three domains,
depending on the structure of their ribosomal RNA,
37
As Michael Pollan puts it, we're only 10% human. Check out his NYTimes article on microbiomes here:
http://tinyurl.com/microbiomes. Gross + cool. –Josephine
Science Power Guide | 10
He saw the cell wall of dried cork cells38
 In 1674, Anton van Leeuwenhoek saw live cells
 He observed many organisms in a sample of pond water under a microscope

Mammalian Cells
Algae
Protozoa
Bacteria
 Robert Brown named and described the nucleus39
He studied van Leeuwenhoek’s drawings extensively
 In 1831, he presented his findings about the nucleus to the Linnean Society of London
 Three scientists jointly developed the cell theory in 183840

Cell Theory
Cells are the basic
units of life
Matthias Schleiden
(Germany)


Cells make up all
living organisms
Theodor Schwann
All cells come from
pre-existing cells
Rudolf Virchow
German physician Robert Koch made numerous breakthroughs in microbiology
 He isolated the causative agent for anthrax in 1875
41
 He also identified microorganisms as the cause of infectious diseases
Germany developed and deployed anthrax and other biological and chemical weapons
in World War I42
 The 1925 Geneva Protocol banned the use of microorganisms in warfare

It prohibited combatants from using infectious diseases as weapons
All You Need to Know About Cells, in a Nutshell
 The Evolution and Diversity of Cells
 Life began on Earth 3.8 billion years ago
38
Unfortunately, as the cells were no longer living, Hooke missed out on all of the good stuff.
Anton von Leeuwenhoek had first observed the nucleus in 1682.
40
USAD issued a correction on July 25, 2013, stating that Rudolf Virchow’s work on the cell theory came much later than Schleiden
and Schwann’s work.
41
This discovery discredited the popular miasma theory
42
USAD states that “it was alleged that the German Army had [used] anthrax”, but most historians today accept that claim as fact,
though it is not well-documented: http://tinyurl.com/mo8gsnf and http://tinyurl.com/kw6y5v9
39
Science Power Guide | 11

Scientists believed that simple molecules formed organic molecules under the
conditions of the early Earth
Carbon Dioxide
Hydrogen Gas
Water Vapor
Methane
Ammonia
Organic Molecules
Amino Acids
Nucleotides
Inorganic Molecules
In the 1950s, Stanley Miller and Harold Urey verified this hypothesis by forming
simple biological molecules in an experiment43
 Prokaryotes are single-cell organisms that exist alone or in clusters and chains
 The word “prokaryote” means “before nucleus”
 Prokaryotes have no nucleus
 These organisms are grouped into either
Archaebacteria or Eubacteria
 Archaebacteria can tolerate hostile living
conditions

Such environments can include hot
springs
 Eubacteria are more common than
Archaebacteria

Therefore, scientists have attended
more closely to Eubacteria
 Prokaryotic cells descended from nucleic acids
enclosed by a plasma membrane
 This membrane consists of a phospholipid
bilayer
44
 Each phospholipid consists of a hydrophilic phosphate “head” and two
hydrophobic fatty acid “tails”

The molecule's “head” faces the bilayer’s extracellular surface

It is exposed to an aqueous external environment

The molecule's “tails” face the bilayer’s intracellular surface

The fatty acids cannot exist in an aqueous solution

The environment between the two phospholipid layers differs from the
external environment
 The plasma membrane serves as the cell’s border
 It also helps maintain equilibrium
 Most prokaryotes have cell walls for protection

43
When the Earth was formed, its atmosphere consisted of methane, hydrogen, ammonia, and water. Miller believed that the Earth also
experienced continuous lightning storms, so he ran an electric current through the set-up.
44
A phospholipid is a type of fat molecule.
Science Power Guide | 12
Chlorophyll-containing bacteria can carry out photosynthesis
45
 This group includes cyanobacteria
 Other types of bacteria feed on chemicals
 The bacteria rely on them for nutrients and energy
 More complex eukaryotes evolved from prokaryotes
 “Eukaryote” means “true nucleus”
 Eukaryotic cells store DNA in the nucleus
 Unlike prokaryotes, eukaryotes contain membrane-enclosed organelles
 Each organelle carries out a specific function
 There are four kingdoms of eukaryotes

Eukaryotic
Kingdoms
Protista
Surrounded by a
plasma membrane
Animalia
Plantae
Fungi
Produce
carbohydrates,
lipids, proteins,
and nucleic acids
Contain genetic
material
Contain subcellular
structures with
distinct functions
 The Architecture of Cells
 All cells share certain characteristics
 Different molecules make up subcellular structures
46
4748
 Lipids are nonpolar and hydrophobic
 These molecules physically separate subcellular structures
 Carbohydrates provide cells with energy
 As cell "workers", proteins participate in many processes
Protein
Processes
Transportation
Recognition
Signal
transmission
Enzymatic
reactions
Nucleic acids contain genetic information
 They are located in the nucleus
 Cells also contain minerals, salts, and vitamins
 These are stored in the cytoplasm
 Prokaryotes contain a variety of cell structures
 The semi-permeable plasma membrane separates the cell from its environment
 However, cells must be able to interact with their environment

45
Scientists believe the oxygen produced by early cyanobacteria led to a dramatic increase in biodiversity and the near-extinction of
oxygen-intolerant forms of life. Thanks to cyanobacteria, humans can flourish on Earth.
46
Nonpolar molecules share electrons equally among the atoms in the molecule. Fats, oil, and gasoline are nonpolar.
47
Water repels hydrophobic, or “water fearing”, molecules. Most hydrophobic molecules are also nonpolar.
48
And most hydrophobic dogs end up ruining our childhood. –Josephine
Science Power Guide | 13

Gates

Molecules travel in and out of the cell through several channels

Each of the channels is a protein embedded in the plasma membrane
Tunnels
Enzymes



49
Receptors
Recognition
Molecules
The plasma membrane encloses a fluid-filled space known as the cytoplasm

Most cell activities take place in this space

The watery (aqueous) part of the cytoplasm is called the cytosol

The cytoplasm refers to the cytosol itself and to all subcellular organelles
floating in the cytosol
Cytosol

Pumps
Subcellular
Organelles
Cytoplasm
The nucleoid contains prokaryotic cell DNA
 This region is circular-shaped
 Several thousand genes control reproduction
and cellular processes
Ribosomes produce proteins
 These organelles consist of ribosomal DNA and
around thirty six proteins
 Thousands of ribosomes exist in the cytoplasm
of prokaryotic cells
Plasmids are circular DNA molecules that exist
outside of the nucleoid
 They can replicate independently of the main
DNA molecule
 Plasmids can house foreign genes

These genes often benefit the host 49

They can jump across bacteria and even
other species
The cell wall provides protection from
environmental changes
 However, they also allow molecules to pass in
and out of the cell relatively freely
 The composition of cell walls varies by cell type

Prokaryotic cell walls consist of a mixture of
peptides and carbohydrates

This mixture is called peptidoglycan

Plant cell walls are made of cellulose
 In certain bacteria, capsules can attach to the
cell wall
For example, foreign genes can provide bacteria with the ability to fix nitrogen, provide resistance to naturally-occurring antibiotics, or
degrade recalcitrant organic compounds when nutrients are scarce.
Science Power Guide | 14
These capsules consist of long carbohydrate molecules known as
polysaccharides

Capsules trap nutrients from the environment

They also protect the bacteria from the host’s immune system50
 Certain appendages control cell movement
 Whip-like flagella allow bacteria to freely move in fluids
 Pili allow bacteria to attach to surfaces

These short, fine appendages are also known as fimbriae
 Eukaryotic and prokaryotic cells differ in specific ways
 Their plasma membranes have different protein structures
51
 Membranes enclose most subcellular organelles in eukaryotic cells
 Several non-membrane-bound structures exist in the cytoplasm

These structures include ribosomes and the cytoskeleton
 Eukaryotes contain a wider variety of cell structures than prokaryotes do
 In eukaryotes, this organelle specialization increases cell efficiency
 The three parts of eukaryotic cells
 Eukaryotic cells contain plasma membranes
 Their structure and function are similar to
Plasma
prokaryotic plasma membranes
membrane
Cytoplasm
 The cytoplasm is located between the plasma
membrane and nucleus
 Some metabolic processes occur directly in the
cytoplasm
Organelles
 One such process is the initial breakdown of
glucose
52
 The cell uses glucose to make ATP
 Most reactions occur in the organelles within the cytoplasm
 The nucleus stores and transmits genetic information to
the rest of the cell
 It is enclosed by a membrane
 The nuclei of all human somatic cells have 46 chromosomes
 Somatic cells include all body cells except egg and sperm
 Each chromosome consists of a compressed DNA molecule bundled with proteins
 Most eukaryotes contain multiple DNA molecules
 In contrast, prokaryotes usually have only one DNA molecule
 Each DNA molecule contains hundreds or thousands of genes
Nucleotides
 Each gene consists of a defined sequence of nucleotides
Genes
 Inside the nucleus is the cell's nucleolus
 This organelle manufactures ribosomal DNA
DNA
 Ribosomes consist of ribosomal DNA strands and
more than 70 types of protein
Chromosome
 Protein synthesis takes place in the ribosomes
 This process of translation occurs after
DNA has been transcribed in the nucleus
 Ribosomes occur in various places in the cell

Eukaryotic cell
50
Capsules can be found in the dreaded E. coli, Streptococcus, and Salmonella bacteria.
Recall that prokaryotic cells do not have subcellular organelles.
52
ATP stands for adenosine triphosphate. It is the main energy source for all known organisms.
51
Science Power Guide | 15
Some float freely in the cytosol

They manufacture cytosolic proteins for immediate use
 Others attach themselves to the rough endoplasmic reticulum

They produce non-cytosolic proteins

The endomembrane system modifies and specializes these proteins

It then sends the proteins to organelles, membranes, or the external
environment
 The endomembrane system consists of four main organelles53

Endomembrane
system
Vesicles
Golgi
apparatus
Endoplasmic
reticulum
Nuclear
membrane
The endoplasmic reticulum (ER) is a group of interconnected membranous vesicles
 It synthesizes, folds, and transports biological molecules
 Rough ER contains many ribosomes

These ribosomes give it a “rugged” texture

Proteins travel to the rough ER after synthesis
 Smooth ER (sER) synthesizes lipids, steroids, and carbohydrates

It also detoxifies poisons that enter the cell
 Vesicles are membrane pockets that transport and temporarily store proteins

The ER, Golgi apparatus, and plasma membrane can form vesicles

The cell first absorbs an external molecule through endocytosis

The portion of the membrane that surrounds the molecule forms a vesicle
 The Golgi apparatus modifies proteins
 This organelle is also called the Golgi
complex or Golgi body
 Membranous sacs receive proteins from the
rough ER
 Then, the Golgi apparatus edits, packages,
and ships proteins to their final destination

Proteins can travel to other organelles

They can also leave the cell through
exocytosis54
 Lysosomes digest nutrients and eliminate waste
 Digestive enzymes packaged in the Golgi
apparatus head here
 Lysosomes consume food through
endocytosis55
 They also eliminate old, worn structures
 This self-eating is called autophagy
 Only animal cells contain lysosomes
 The cytoskeleton has several roles within the cell

53
“Nuclear envelope” (used by USAD on page 16) and “nuclear membrane” are interchangeable. They both refer to the membrane that
encloses the cell’s nucleus.
54
In exocytosis, a vesicle fuses with the plasma membrane and releases its contents into the environment.
55
In the process of endocytosis, cells engulf and absorb molecules that cannot pass through the plasma membrane.
Science Power Guide | 16
Support and
maintain cell shape
Ease protein
transport within
the cell
Ease cellular
movement
Roles of the
Cytoskeleton
Interact with
extracellular
anchor structures
Anchor internal
organelles

It consists of three main parts56
Microtubules
Intermediate Filaments
Largest of the
cytoskeletal elements
Cage-like filaments
Akin to strings of beads
Act as the cell s skeletal
system and provide
intracellular support
Configured similarly to
the steel cables of
suspension bridges
Thinnest of the
cytoskeletal elements
Transport molecules
within the cell
Stabilize and maintain
the position of
organelles
Provide strength,
mobility, and shape for
the cell
Serve as spindle fibers
during meiosis
Produce cellular
movement by acting as
cilia and flagella
56
Microfilaments
In the illustration, both phagocytosis and pinocytosis are specialized forms of endocytosis.
Involved in phagocytosis
(cell eating), pinocytosis
(cell drinking), muscle
contraction, and cell
movement
Science Power Guide | 17
 Cilia and flagella participate in cell movement and surface adhesion57

The cell moves when bundled microtubules slide together
Small
projections from
the cell's surface
Used by cells in
the trachea and
fallopian tubes
One or two tails
Cilia
Move by lashing
back and forth
Used by sperm
cells
Flagella
 Mitochondria and chloroplasts produce a cell’s energy

One theory suggests that mitochondria and chloroplasts descended from ancient
prokaryotes
 Some early prokaryotes may have lived symbiotically within eukaryotic cells
 Konstantin Mereschkowski proposed this endosymbiosis theory in 1905
Mitochondria
Mitochondria and
chloroplasts
Chloroplast
Found in animal
cells
Replicate
independently and
survive on their
own
Found in plant and
photosynthetic
protist cells
Produce adenosine
triphosphate (ATP)
through cellular
metabolism
Contain their own
circular DNA
separate from the
nucleus
Contain
chlorophyll
Contain
prokaryotic-like
ribosomes
Transform solar
energy into ATP
Enclosed by a
double-layered
membrane
 In plants and protists, central vacuoles perform the duties of the lysosome
57
USAD mentions that cilia and flagella play a role in surface adhesion on page 17. However, specialized adhesive molecules “allow cells
to maintain contact…with structures in the extracellular matrix”. (Nature)
Science Power Guide | 18
Support the cell
wall
Eliminate excess
water
Maintain cellular
rigidity
Central
Vacuole Jobs
Ensure balanced
levels of salt in
cytoplasm
Store wastes,
toxins, and
pigments
 Certain organelles perform four key tasks during cellular reproduction
DNA replication

Organelle
duplication
Relocation of
duplicated
organelles
Distribution of
duplicated
organelles
Centrosomes serve as microtubule organizing centers
 A pair of centrioles within each centrosome anchors the microtubules
 Microtubules produce spindle fibers

These fibers pull the chromatids and centrosomes further apart
 In plant cells, microtubules attach to other organelles instead of centrosomes
 Genetic Material and the Life Cycle of an Organism
 Most cells of a given species have identical genetic information
 For example, almost all human cells have 3.1 billion
nucleotides contained in 22,000 genes
 Each gene has about 3,000 nucleotides
 One gene codes for a protein with less than 1,000
amino acids
 However, not all genes are expressed or activated
 Only a few genes in the adult human body control
cell formation
 These cells make up less than 5% of the entire human
genome
 Reproduction transfers genetic material from parent to
offspring
 This process ensures the survival of the species
 Asexual reproduction can occur in both prokaryotes and
eukaryotes
 This type of reproduction produces offspring identical to
the parents
 Prokaryotes reproduce through binary fission
Science Power Guide | 19

DNA
replication
creates two
DNA loops
The parent cell clones itself, forming an identical daughter cell58
The loops
attach to the
plasma
membrane

The plasma
membrane
pinches and
splits
The cell
expands and
elongates
Two identical
daughter cells
are formed
Scientists consider binary fission a simple form of reproduction
Simple cytoplasmic structure
Absence of membrane enclosing
DNA
Single DNA molecule
Binary fission
In an optimal environment, a bacterium can divide in 20 minutes

Over 10 hours, one bacterium can become 1 billion
 However, eukaryotic cell division is more complex than prokaryotic cell division

Presence of nuclear envelope surrounding
chromosomes
Presence of multiple chromosomes
What makes eukaryotic cell division
complex?
Larger number of subcellular organelles

Creation of a new cell wall in some organisms
Eukaryotes reproduce asexually in a variety of ways
Fission
Budding
Eukaryotic
asexual
reproduction
Mitosis
Regeneration
 All eukaryotic cells follow the cell cycle

58
In unicellular eukaryotes, the cell cycle creates a new generation of individuals
Let's hope the Kardashians don't figure out binary fission. –Josephine
Science Power Guide | 20

It also enables many important biological processes
Budding
Fission
Embryonic
development
Regeneration
Growth
Renewal
Replacement of
dead cells
The cycle begins with the synthesis of molecules
 It ends when two daughter cells are formed
 One full cycle lasts 20 to 24 hours
 During the cycle, the cell constantly grows and
replicates

Gaps occur between the phases of the cell
cycle
 The cell cycle takes place in two main stages
 The cell spends 90% of its life in interphase
 During interphase, the cell replicates each
organelle and DNA molecule
59
 The cell seeks to maintain homeostasis
 A cell spends the other 10% of its life in mitosis
 The three stages of interphase occur first
60
 Organelles replicate in the G1 phase
 The G1 phase involves constant RNA and
protein synthesis

These processes produce the proteins, lipids, and carbohydrates required to
assemble organelles
61
 The cell’s genome replicates in the S phase
 During this phase, the cell’s 46 chromosomes double to 92

The cell’s 6.2 billion nucleotides increases to 12.4 billion
 Each chromosome becomes two sister chromatids

The centromere and other adhesive proteins link the two chromatids
 The replicated organelles assemble during the G2 phase
 The four stages of mitosis occur after interphase62

59
Homeostasis allows the cell to maintain a stable internal environment in a changing external environment.
The G stands for “gap”
61
The S stands for "synthesis"
62
The kinetochore is a protein structure where spindle fibers attach during late prophase.
60
Science Power Guide | 21
Early Prophase
The dispersed sister
chromatids condense
The nuclei disassembles
rRNA production stops
Spindle microtubules from
the microtubule organizing
center push away the two
centrosomes
The centrosomes migrate
towards the poles
Late Prophase (Prometaphase)
The nuclear envelope
breaks into vesicles
Spindle microtubules
interact with the
chromosomes
Each sister chromatid
builds a kinetochore near
the centromere
The kinetochore
microtubules separate the
sister chromatids
Polar (or non-kinetochore)
microtubules begin to
elongate the cell and push
the centrosomes to the
opposite ends of the cell
Metaphase
All chromosomes line up in the metaphase
plate in the middle of the cell
The kinetochore microtubules pull the sister
chromatids towards the cell's center
Polar microtubules continue to elongate the
cell
Anaphase
Adhesive proteins bonding the
sister chromatids turn off
The centromere splits in two, and
the chromatids are now two
chromosomes
The kinetochore microtubules
pull the chromosomes towards
the poles
Polar microtubules continue to
elongate the cell
Telophase
The cell seeks to return to
equilibrium
Chromosomes unwind and
disperse
The nucleolus and nuclear
envelope reassemble
The spindle microtubules and
centrosomes break down
Science Power Guide | 22



Cytokinesis is the final stage of mitosis
63
 “Cytokinesis” means “cell move”
 During this stage, the plasma membrane
splits in two, forming two separate cells
In animal cells, cleavage breaks the plasma
membrane apart
 First, microfilaments and microtubules
contract

This contraction creates a cleavage
furrow
 Then, the cleavage furrow moves inward

The plasma membrane breaks in two
 Finally, the cell becomes two daughter
cells
In plant cells, vesicles containing cellulose
assemble and fuse together
 This process forms a cell plate
 The cell plate then adds on
polysaccharides and proteins to form a
cell wall
 Sexual reproduction
 Sexual reproduction allows natural selection
 A species in a constantly changing
environment requires genetic diversity to
survive
 99.9% of eukaryotic organisms reproduce
sexually
 Cells first exchanged genetic material
two billion years ago
 This gene shuffling spreads beneficial
traits and eliminates disadvantageous
traits
 Protists were the first organisms to reproduce
sexually
 Several modern prokaryotes divide by
mitosis under ordinary conditions
64
 They switch to sexual reproduction in a hostile or unstable environment
 When a multicellular organism reproduces sexually, germ cells transfer genetic material
from parent to offspring
 These immature germ cells contain 46 chromosomes
 This number makes them diploid cells
 Most somatic cells are also diploid
 Germ cells move to the gonads when the organism is an embryo
 Once in the gonads, the cells are called immature or gonadal gametes
63
64
Also one of the Jean Grey's lesser-known superpowers.
The genetic diversity produced by sexual reproduction would help ensure the species’ survival.
Science Power Guide | 23
Male
Germ cells:
spermatogonia






Female
Gonads: testes
Germ cells: Oogonia
Gonads: ovaries
The cells remain inactive in the gonads
until puberty
 However, in some organisms, female
gametes may begin to divide while still
in the embryo

This early division occurs in
humans65
Once the offspring reaches puberty,
reproductive hormones signal the
immature gametes to start dividing
Germ cells mature into gametes by
dividing twice in a process called
gametogenesis
 The newly created gametes are haploid
cells

They contain only 23
chromosomes66
During fertilization, two gametes unite to form a fertilized egg
 This zygote contains half of the father’s and half of the mother’s genome
The zygote turns into stem cells after it has divided by mitosis five or six times
 These cells can become any of the 260 types of adult human cells
The zygote continues to divide, creating the 50 trillion somatic cells found in adult
humans
Haploid sperm and
egg cells merge
during fertilization
The diploid zygote
contains genetic info
from the male and
female parent
Through mitosis, the
zygote creates the
50 trillion adult
human somatic cells
 Gametogenesis requires gametes to divide by meiosis67


65
The interphases of mitosis and meiosis are nearly identical
 However, mitosis involves the random movement and distribution of chromosomes
 In contrast, chromosomes that carry the same type of genetic information will move
together in meiosis I

These chromosomes are known as homologous chromosomes

They come in pairs, one from both the maternal and paternal sides
Meiosis has two major phases, meiosis I and II
 Prophase, metaphase, anaphase, and telophase each take place twice
Scientists estimate human females produce as many as 700,000 “primary oocytes” by the time they are born. Only 400 of these oocytes
will go through meiosis II and become fully developed egg cells—about 30 years of ovulation for women, give or take a few pregnancies.
66
Think of “hap” as half, as haploid cells have half a full set of chromosomes. “Di” means two, as diploid cells have 23 pairs of matching
chromosomes.
67
Coolest Crash Course videos ever: http://tinyurl.com/nrucgn5 (mitosis) and http://tinyurl.com/b8k3naw (meiosis)
Science Power Guide | 24

The events of prophase I differentiate mitosis and asexual reproduction from meiosis
and sexual reproduction
 It is the longest phase of meiosis

This phase can take up to 90% of the total time required for cell division
Chromatin condensation
Nucleoli disappearance
Cellular processes in meiosis prophase I
Nuclear envelope fragmentation
Spindle fiber formation
During prophase I, homologous chromosomes
pair up

Each chromosome consists of two
connected sister chromatids

The two pairs of sister chromatids form a
“double X” pattern called a tetrad
 Non-sister chromatids intertwine at regions
known as synapses

The chromatids break and reconnect,

During this process, they exchange
genes

This random “crossing over” of genetic
information fosters genetic diversity in the
daughter cells
In metaphase 1, the pairs of homologous
chromosomes move to the metaphase plate68
 One chromosome faces each pole of the cell
 The tetrads orient randomly
 Microtubules attach to the kinetochore of each
chromosome
In anaphase I, the pair of homologous
chromosomes split and migrate to the poles
 Spindle fibers pull them
 Sister chromatids are still attached by the centromere

Therefore, they move together
In telophase I, chromosomes move towards the poles
 The nucleus of the daughter cells will later form at this site
 The nuclear envelope reforms briefly
 Chromosomes begin to disperse
69
 Cytokinesis initiates
70
 At this point, each pole can be classified as haploid

However, the chromosomes do not re-replicate before moving on to meiosis II71
Meiosis I and II are nearly identical





68
This is a region of the cell equidistant from the two spindle poles. Think of the metaphase plate as the cell’s equator.
Recall that cytokinesis is the final stage of cell division, when the plasma membrane splits in two.
70
Remember that haploid cells have 23 chromosomes, or half of a full set.
71
This lack of re-replication causes the four daughter cells to be haploid.
69
Science Power Guide | 25

Nuclear
envelope
disappears
Spindle fibers
form and
attach to
kinetochores
Prophase II
However, the sister chromatids in meiosis II are not identical

Crossing over in meiosis I results in non-identical sister chromatids
Metaphase
II
Sister
chromatids
align at the
metaphase
plate
Centromeres
split
Each
chromosome
towards the
poles
Anaphase II
Telophase II
Chromosomes
decondense
Nuclear
envelope
reforms
Cytoplasm
divides
Meiosis II
ends with
four haploid
daugher cells
Cytokinesis
 When male and female gametes join, they form a zygote
This zygote divides into increasing specialized cells through mitosis
During its first five or six divisions, the zygote divides into totipotent cells72
 These cells can become any of the 260 types of human cells
73
 Further cell division produces pluripotent cells
74
 These cells can form any of the three germ layers
75
 The three germ layers can form any type of human tissue
 As cells continue to differentiate, they can form only certain types of specialized cells
 These cells are described as multipotent

For example, multipotent bone marrow stem cells can become any of the 12
types of blood cells

They cannot differentiate into as many cell types as embryonic stem cells

By this point, multipotent cells are migrating to their future organ location
 All multicellular organisms contain stem cells
76
 Unlike regular cells, these cells can divide infinitely
 They can also become one of many types of cells
 Embryonic stem cells are pluripotent
 Adult stem cells are multipotent
 Daughter stem cells can either remain stem cells or specialize
 Stem cells can continue dividing or enter the pool of inactive, reserve stem cells
 Scientists have recently identified certain genes that control stem cells


72
Totipotent comes from the Latin word “totus”, meaning “entire”, and “potential”, or “power”. The zygote has the ability to become
any cell—effectively demonstrating its full extent of power.
73
This comes from the Latin “plurimus”, meaning “very many”.
74
These are the endoderm (stomach, intestines, lungs), mesoderm (muscle, bone, and blood), and ectoderm (skin and nervous system).
Biologists can differentiate between animal phyla (the taxonomic classification directly under kingdom) by the number of germ layers in
the embryo. For example, chordates have all three germ layers, but sponges only have one.
75
Note that both totipotent and pluripotent cells can produce all 260 human cell types. However, totipotent cells can become the
placenta or other supporting cells in the mother’s uterus. Therefore, they can give rise to a whole new organism if placed in another
uterus, while pluripotent cells will not.
76
When DNA replicates, around 100-200 nucleotides are lost at the tip of the chromosome. During the first several replications, noncoding regions known as telomeres are eliminated, ensuring that the coding regions of DNA remain intact. After thousands of
replications, the chromosome will run out of telomere and cease to divide further. Stem cells have an enzyme known as telomerase that
continually add fragments of telomeres to chromosomes, ensuring their ability to replicate indefinitely.
Science Power Guide | 26

They hope to discover a method of transforming adult somatic cells to pluripotent stem
cells
 This transformation would allow doctors to “create” new cells to replace worn
tissues

For example, in the future scientists may be able to stimulate stem cells to
become cardiac muscle cells

These cells would replace damaged cells in patients with heart disease
 Four Sources of Genetic Variation
 Mutation drives genetic variation
 A mutation is a change in the order of nucleotides
in the DNA molecule
 Some mutations are harmless, while others can be
deadly
 Some may eventually form a new species
 Crossing over also leads to genetic variation
 During meiosis prophase I, similar chromosomes
exchange genetic material
 This process allows the mother and father to
each pass on certain traits
 Crossing over can occur up to 60 times in a human
germ cell during meiosis
 Meiosis metaphase I produces even more genetic
variation
 In this phase, chromosomes shuffle around and
combine randomly
 With 46 chromosomes, humans can produce 64
trillion possible chromosomal combinations
 Random mating and fertilization also produces
genetic variation
 Male gonads make 50 million sperm cells per day
 Female ovaries hold one million reserve egg cells
 Any of these can fuse together during conception
 Somatic cells grouped by frequency of division
 Certain cells do not need to divide as frequently
as others
 The human body cannot produce enough
energy to keep 50 trillion cells dividing
constantly
 Dividing cells continually undergo interphase
and M phase
 Cells of this type die frequently
 Only 10% of these cells divide at a given
point in time
 This low percentage means the tissue can
continue to function normally
 Non-dividing cells exist permanently in the G0
phase
Translocation
Inversion
Mutation types
Substitution
Addition
Deletion
Science Power Guide | 27
This phase is not part of the cell cycle
 These cells do not undergo division under normal conditions
 They must function continually for the body to operate properly
 If heart and brain cells ceased to function in order to conduct cell division, the entire
human body would shut down
 Reproductively dormant cells normally reside in the G0 phase
 Under certain circumstances, these cells can re-enter the cell cycle
 For example, wound healing activates dormant cells

Dividing cells
Reproductively dormant
cells
Non-dividing cells
Skin cells
Nerve cells in the brain
Intestinal epithelial cells
Hair cells in the ear
Uterine endometrial cells
Heart muscle cells
Liver cells
Lens cells in the eye

Other organisms contain reproductively dormant cells
 For example, plant embryos in seeds do not actively divide
 These cells will only reproduce in a favorable environment
Increasing levels of sunlight
Fire
Possible conditions for a favorable
reproductive environment
Temperature

Presence of chemicals
Favorable environmental conditions will stimulate hormones within the cell
 These hormones signal the cell to re-enter the cell cycle
 Control of the Cell Cycle
 Checkpoints in the cell cycle ensure that cells reproduce only in a suitable environment
 The cell monitors certain characteristics
 These characteristics have to pass inspection before the cell can enter the next
phase of the cell cycle
G1 phase
Cell Size
Nutrient availability
Growth
DNA damage
G2 phase
M phase
Cell size
Spindle fiber attachment
to chromosomes
DNA replication
Science Power Guide | 28
Checkpoint malfunctions lead to
uncontrolled cell growth
 Uncontrolled cell growth is better
known as cancer
 Most human cancers form when genes
related to the cell cycle mutate and
malfunction
 Without checkpoints in the cell cycle,
cells will proliferate rapidly77
 The cell cycle is missing “roadblocks”
that regulate cell division
 Proteins that inhibit mitosis can fail to
function properly
 Proteins that promote mitosis can be
over-expressed

Protein overexpression can
transform regular cells into
cancerous cells
78
 Normal genes can also mutate into oncogenes
 These genes stimulate excess cell growth

77
Interestingly enough, a cancer cell is the only other type of cell that can activate telomerase, allowing the cell to divide indefinitely (see
footnote 65).
78
The root “onco” comes from the Greek word “onkos”, meaning mass or bulk (i.e. a tumor). Thus, oncology is the study of cancer.
Science Power Guide | 29
THE PATTERN OF INHERITANCE
POWER PREVIEW
POWER NOTES
Mendel’s groundbreaking research on pea plants, based on the
principles of probability, provided the foundation of modern
genetics. The scientific world applies his three laws widely,
especially in the study of genetic diseases. Punnett squares
allow scientists to calculate the odds of inheriting a trait from
parents, while genetic testing enables quick detection and
treatment of inherited diseases and disorders.
 According to the USAD outline, 17-18
questions (35%) should come from Section
II.
 21 questions (42%) come from Section II
on the USAD Science Practice Test.
 Section II covers pgs. 30-49 of the USAD
Science Resource Guide
Mendel’s Grand Experiment
 Mendelian Genetics
 Charles Darwin observed and collected data in the Galapagos Islands for several years
79
 He grew to doubt the prevailing theory of blending inheritance
th
 19 century scientists most commonly accepted blending inheritance as an
explanation for inherited traits
 Darwin's contemporary Gregor Mendel sought to solve the mystery of genetic inheritance
definitively
 Mendel’s career goal was to become a teacher
80
 He held a part-time position as a substitute teacher in a Brno monastery
 At the same time, he was preparing to become a priest
 After Mendel failed the teacher certification exam once, his abbot sent him to the
University of Vienna81

Mendel studied numerous
subjects at university
Botany

After failing the teaching
exam for the second time, he
remained at the monastery
Physics
Mathematics
for the rest of his life
Mendel's

In 1868, he was elected
Studies
prelate82
 In 1854, Mendel embarked on a
plant hybridization experiment
Fertilization
Cell theory
83
 He first had to gain the abbot’s
permission
 Mendel’s study had two main goals
79
Remember this theory all the way back in Section 1? According to the theory of blending inheritance, offspring inherit a mix of their
parents’ traits.
80
Recall that Brno was a city in Austria-Hungary.
81
For chronological reference, Mendel failed the certification exam for the first time in 1850, entered the University of Vienna in 1851,
and failed the exam again in 1856.
82
Prelates are high-ranking church officials, such as bishops and abbots, who have the power to execute ordinary laws.
83
The abbot is the head of a monastery.
Science Power Guide | 30
Study transmission of traits
over generations

Produce a profitable crop
for the monastery
Medel used the garden pea (Pisum sativum) for his experiments
84
 This seemingly wise decision may or may not have been intentional
Easy to grow
Reproduce quickly
Why pea plants?
Easy to manipulate pollination

Easy to describe and
distinguish traits
He chose seven out of 34 traits

These traits vary from strain to strain
Pod shape
Flower color
Flower position
Plant height
Pod color
Pea shape
Pea Plant Traits
Pea color
Each trait comes in two easily distinguishable forms

Using these traits simplified Mendel’s large-scale experiment

He could easily interpret and analyze the results
Mendel analyzed plants that differed only in one trait over multiple generations
 He performed the first documented monohybrid cross

Dihybrid crosses analyze two traits simultaneously
Mendel was also the first scientist to apply mathematical modeling to genetics
85
 Principles of probability allowed him to predict and analyze the traits of future
generations

He had learned these principles at the University of Vienna



84
In this case, the abbot may have “encouraged” him to experiment with pea plants to ensure the monastery’s economic survival, or
Mendel may have chosen the pea plant because it was the only plant available at that time. Mendel may have also known that pea plants
possessed traits conducive to scientific experimentation. Ultimately, we just don't know.
85
For the math nerds out there: Mendel used the binomial theorem to expand    with n=2.
Science Power Guide | 31
Multiplication Rule
If two events are independent, then the probability that
they both occur is the product of the probabilities of each
occurring
•     ∗ 
Addition Rule
If two events are mutually exclusive, then the probability
of either event occuring is the sum of the individual
probabilities
•    
Binomial Theorem
•    ∗       2   
Using thousands of pea plants provided enough experimental data to draw
statistically significant conclusions
Mendel observed three generations of pea plants
86
 The first generation is the true-breeding variety

This is the P generation
 The second generation is the F1 generation

The “F” stands for “filial”, which derives from the Latin for “son”

If the F1 plants self-fertilize, they produce the F2 generation


P generation
F1 generation
F2 generation
Mendel noticed that the F1 generation only inherited one trait from the
parent
 The F2 generation, however, displayed both traits

The F1 trait occurred in a 3:1 ratio

Mendel suspected that one trait could be dominant over the other
In one of his experiments, Mendel crossed a purebred white flower plant with a
purebred purple-flower plant
87
 He sprayed the pollen from the purple flower’s stamen on the white flower’s stigma

All of the F1 flowers were purple

When Mendel reversed the experiment, the F1 flowers were still purple

This result showed that flower color was not a sex-linked trait
Mendel noticed that his experiment results contradicted the commonly accepted theory
of blending inheritance
 The purple F1 flowers were identical to the parent purple flower

They did not display a blend of traits
 He concluded that the purple flower color trait was dominant over white
By the binomial theorem88, purple flowers will occur ¾ of the time and white flowers ¼
of the time




86
True-breeding means purebred, or an organism that has a homozygous genotype.
The stigma and stamen are the plant’s male and female reproductive organs, respectively.
88
The binomial theorem is also the basis for the all-so-important Hardy-Weinberg theorem, which will be discussed in the next section.
87
Science Power Guide | 32
Mendel counted 705 purple-flowered
and 224 white-flowered plants in the
self-pollinated F2 generation

This resulted in a 3.1:1 ratio89

These results held for the other
six traits of Mendel’s experiments
Mendel died in obscurity in 1884
 He was convinced that his work
would “be appreciated before long
by the whole world”90
 Today, we recognize that Mendel’s
work demonstrated the principles of
the scientific method


Make initial
observations
Draw databased
conclusions
Design
experiments
Formulate
testable and
falsifiable
hypotheses
Statistically
analyze results
An Overview of Mendelian Genetics
 The Basics
 Chromosomes occur in the nucleus of most sexually reproducing species
 Each cell in a species contains a specific number of chromosomes
 Each chromosome is a DNA molecule that houses many genes

Each gene codes for one or more proteins

Each protein controls the expression of a trait

This trait can be expressed externally or internally through metabolic
reactions91
Two main categories of chromosomes
89
Non-sex chromosomes (autosomes)
Sex chromosome
Chromosomes 1-22
Chromosome 23
But any mathematician and physicist will tell you the oh point one makes such a big difference - Eric
Quoted also by USAD, this phrase comes from the 2008 edition of Biology, by Robert Brooker, et al.
91
Metabolic reactions are chemical processes that allow a cell to sustain life.
90
Science Power Guide | 33
 Diploid cells contain paired chromosomes
These pairs are called homologous chromosomes
 They contain corresponding genes at any given
location
 However, the sequence of nucleotides does not
have to be identical
 The two corresponding genes are alleles

Alleles determine the organism’s
genotype
 Alleles can be dominant or recessive

Capital letters represent dominant alleles

Lowercase letters represent recessive
alleles92
 Recessive alleles indicate malfunctions in the
coded protein

The physical trait controlled by that
protein is not expressed correctly93
 Alleles can also be homozygous or
heterozygous

Homozygous alleles have identical nucleotide sequences

Heterozygous alleles have different nucleotide sequences
Genotypes control the external expression of traits
 These traits are known as phenotypes
 If the chromosome contains at least one dominant allele, the organism will express a
dominant phenotype
 If the chromosome has two recessive alleles, the organism will express a recessive
phenotype94
Mendel’s Laws
According to the law of dominance, only dominant traits will appear in the F1 generation
According to the law of segregation, the pair of alleles that determine a specific genotype
separate and re-combine during fertilization
95
 The law explains the process of meiosis
 Mendel proposed that pairs of alleles segregate during gamete formation and
recombine during fertilization





Gamete Formation
Homologous chromosomes
separate during anaphase I
92
Alleles are split
Spem and egg cells become
haploid
If the genotype for pea color is given by the letter “A”, then a capital “A” would represent the dominant allele (yellow), while a
lowercase “a” would represent the recessive allele (green).
93
For example, albinos inherit a recessive allele that causes the skin-producing pigment melanin to be produced incorrectly. I’ll explain
the molecular basis behind this statement in Section III.
94
If the letter “a” represented an allele, then “AA” would be a homozygous dominant genotype, “Aa” would be a heterozygous dominant
genotype, and “aa” would be a homozygous recessive genotype.
95
Meiosis was first observed in sea urchin eggs by the German biologist Oscar Hertwig in 1876.
Science Power Guide | 34
For example, if a spermatogonia carries the genotype AA, then each sperm cell will
end up carrying an A
 According to the law of independent
Probability of
Phenotype
Occurrence
assortment, alleles for different traits segregate
independently
9
3 3
Yellow and Round
∗ 
4
16
4
 To test this concept, Mendel conducted a
3
1 3
dihybrid cross96 of pea shape and color
Green and Round
∗ 
4 4 16
 From previous crosses, he knew that
1 3
3
Yellow and Wrinkled
∗ 
round and yellow were dominant over
4 4 16
wrinkled and green, respectively
1
1 1
Green and Wrinkled
∗ 
 Mendel first crossed purebred plants
4 4 16
with round, yellow seeds and plants
with green, wrinkled seeds,

The entire F1 generation had
round and yellow seeds
 This dihybrid cross resulted in an
approximate 9:3:3:1 phenotype ratio

The results convinced Mendel
that the alleles for the two
traits behaved independently
 Mendel developed his three laws long
before modern understanding of genetics
 His results disproved the theory of
blending inheritance
 Genes, not traits, pass from parent to
offspring
 Mendel also realized that alleles usually
come in two forms97
 However, mutations and
evolutionary adaptation allow
populations to develop multiple
form of alleles

He predicted that one allele would
dominate over the other

Dominant alleles produce
functioning proteins, while
recessive alleles do not

Proteins ultimately determine how traits are expressed

Mendel theorized that alleles for different traits sort into gametes independently

Coincidentally, all seven of Mendel’s selected traits were on different
chromosomes

The law of independent assortment does NOT hold true for linked genes

Linked genes are found in close proximity to each other

The 9:3:3:1 phenotype ratio does not apply for linked genes

96
97
Mendel crossed a maximum of three traits at the same time, or a trihybrid cross. Just try filling in that Punnett square.
This refers to the dominant and recessive forms of the allele.
Science Power Guide | 35
Mendel developed
his three laws before
scientists knew that
genes exist
genes have multiple forms
chromosomes sort during meiosis
meiosis transforms diploid germ cells to haploid
gametes
genes are found in chromosomes
So What?
 The Significance of Mendel’s Laws
 Most human traits controlled by a single gene are harmless
Earlobe attachment

Widow's Peak
Hitchhiker's Thumb
However, many gene mutations can cause disease or death
98
 At the 2003 conclusion of the Human Genome Project , scientists agreed that all
diseases were linked to genetics
 Understanding these diseases enables scientists to develop effective genetic
screening, diagnosis, and treatment
“All diseases have a genetic component, whether inherited or resulting from the body's
response to environmental stresses like viruses or toxins.”
- The Human Genome Project

Cystic fibrosis affects one in 2,500 people of Northern or Central European descent
99
 It is the most common deadly inherited disease in America that affects Caucasians
A gene that
codes for a
channel protein
on the cell
surface mutates
The protein
channel ceases
to function
Thick and sticky
mucus lines the
lungs and
digestive system
Lung infections
and digestive
problems result
 One in 400 African-Americans suffers from sickle cell anemia

98
99
It is the most common genetic disease in the United States
This multi-year project brought together the work of many scientists to map the human genome. We'll discuss it in Section III.
The mutation that causes cystic fibrosis primarily affects the lungs, pancreas, and exocrine glands.
Science Power Guide | 36
A point
mutation occurs
A protein in the
hemoglobin
molecule folds
incorrectly
Red blood cells
form a sickle
rather than a
doughnut
Red blood cells
can no longer
squeeze
through
capillaries
Lack of oxygen
leads to
multiple organ
failure
 Tay-Sachs disease affects one in 3,500 Ashkenazi Jews100
Single gene
mutation alters
a lipid
metabolism
enzyme
Abnormal lipid
coats surround
brain cells
The brain
cannot transmit
neural impulses
correctly
Paralysis,
blindness, and
deafness can
result
 Cystic fibrosis, sickle cell anemia, and Tay-
Sachs are all homozygous recessive
diseases
 Carriers are heterozygous for the
required gene
 They do not have the disease but
can pass it on to their children
101
 The ratio between normal
and
diseased individuals is 3:1
 Genetic counselors seek to identify
parents’ genotypes before the parents
choose to have children
 If the parents are carriers for a
genetic disease, the counselor can inform
them about the risk of passing the disease
onto their children
 Diversity in the Pattern of Inheritance
 Complete dominance occurs when the
heterozygote dominant phenotype matches the
homozygote dominant phenotype102
 When homozygous purple and white flowers
cross, they produce only purple offspring
 Purple dominates over white
 A homozygous and heterozygous dominant
purple flower will produce the same purple
flower offspring
 On the other hand, incomplete dominance occurs
when no single trait is dominant or recessive
100
Ashkenazi Jews trace their ancestry to Central and Eastern Europe. 80% of Jews worldwide are Ashkenazi, including both DemiDec's
Editorial Director and Alpaca-in-Chief.
101
USAD uses “normal” to refer to individuals with a homozygous dominant or heterozygous genotype.
102
In other words, there are only two possible phenotypes (dominant and recessive). For example, complete dominance controls the
inheritance for human earlobe attachment. Offspring can have either free (dominant) or attached (recessive) earlobes, but not semiattached or partially attached earlobes.
Science Power Guide | 37
The offspring’s traits represent a “blend” of both parents103
 For example, when homozygous white and red flowers are crossed, they produce a
range of pink-colored offspring
 In this way, incomplete dominance is similar to blending inheritance
 Familial hypercholesterolemia (FH) passes through genes controlled by incomplete
dominance
 FH results in abnormally high levels of blood cholesterol
 Patients can have heart attacks in their twenties
 One in 500 Americans carries this recessive allele
 Cholesterol is a lipid molecule found in all cellular membranes

Gonadal cells use cholesterol to synthesize sex steroids104

However, cholesterol is not blood-soluble

The liver must package it with a protein for transport to the rest of the body

This protein-cholesterol molecule is called low-density lipoprotein (LDL)
cholesterol
 Each cell contains LDL receptors that recognize and process LDL

Once an LDL molecule reaches the cell, it clusters near coated pits and is
absorbed by the cell
 If the LDL receptor gene mutates, the protein product cannot bind, group, and
absorb LDL for transport to cells

Instead, LDL remains in the bloodstream, clogging arteries

Hypercholesterolemia and cardiovascular disease result
 Certain regions of the LDL molecule are responsible for the individual steps of LDL
absorption

Mutations in any part of the LDL receptor molecule will prevent LDL uptake

The protein product will be unable to bind, group, and absorb LDL for
transport to cells
 In 1970, the Southwest Medical Center in Dallas admitted 14-year-old J.D.

His cholesterol level was over 800 mg/dl (milligrams per deciliter)

This level was four times higher than the cholesterol level of a typical young
adult

J.D.’s family had a history of high cholesterol

However, not all family members had high cholesterol levels

Doctors suspected that a certain gene could directly control cholesterol levels

They discovered that no LDL cholesterol could enter J.D.’s cells

J.D. died before he turned 30

FH indicates that mutations of a single gene can lead to a wide range of trait
expressions
 Co-dominance occurs when neither allele dominates over the other
 Both alleles will be expressed as a result
 Co-dominance can control the inheritance of certain blood types
 The surface of red-blood cells contains a membrane protein with two different forms of
sugar molecules attached to the protein’s exterior
 This extracellular part of the protein is known as glycoprotein
 Doctors once thought that all human blood was identical
 No one could explain why blood transfusions caused acute reactions and death

103
104
Just think of black and white mixing to produce different shades of grey.
Steroids do have a good use after all, I guess, much like mothballs and global warming - Eric
Science Power Guide | 38



The Austrian scientist Karl Landsteiner105 (1868-1943) discovered the ABO blood
typing system in 1900
 Landsteiner noticed the red blood cells of
certain people clumped with the serum106 of
others

This clumping is known as agglutination
 Landsteiner developed the ABO blood typing
system based on the agglutination of different
types of blood

He won the 1930 Nobel Prize in Medicine
for this discovery
Blood compatibility depends on the relationship
between antigens and antibodies
 The surface of red blood cells can contain Aantigens, B-antigens, both, or neither
 Blood also can contain anti-A antibodies, antiB antibodies, both, or neither
 Anti-A antibodies will attack A antigen

Red blood cells with A antigen will clump
together, triggering cell destruction

This agglutination also occurs when
anti-B antibodies107 and B antibodies
Anti-A
A antigen
come into contact
antibodies

In both cases, clumping will lead to
severe anemia108, oxygen deficiency,
and death
Four blood types lead to eight total possible genotypes
Blood
Type
Possible
Genotype
Antigens in
Red Blood Cell
Antibodies
in Serum
Can Donate
Blood To
Can Receive
Blood From
A
AA or AO
A
Anti-B
A, AB
A, O
B
BB or BO
B
Anti-A
B, AB
B, O
AB
AB
A and B
None
AB
AB, O
O
OO
None
Anti-A and
Anti-B
A, B, AB, O109
O


105
Type AB blood is an example of co-dominance110

Both the A and B antigens are expressed on the red blood cell surface
When blood transfusions occur, blood types must be matched correctly
Check out his facial expression. I would not want to be running into this guy in a dark alleyway at night. - Eric
Serum refers to plasma (the liquid part of blood) without any clotting proteins
107
What's a pessimist's blood type? B- . –Josephine
108
Individuals with anemia have a lower-than-normal red blood cell count
109
This is why people with type O blood are known as “universal donors”
110
In ABO blood typing, A and B both dominate over O. In order to have type O blood, an individual must inherit two recessive (O)
alleles.
106
Science Power Guide | 39
A patient who receives incompatible blood may suffer transfusion shock or death
 Courts used ABO blood typing to identify specific phenotypes in paternity legal cases
 DNA testing superseded this technique in 1984
 The famous 1943 Barry/Chaplin case involved blood testing

Joan Barry accused actor Charlie Chaplin111 of fathering her child

Blood tests excluded Chaplin as the father

The court refused to accept this evidence

Chaplin was forced to pay child support

Public outrage at this trial led to new laws
allowing blood tests as court evidence
 The Rh factor is also an important surface antigen
 It was first identified in rhesus monkeys
 This factor determines the “+” or “-” sign after
the ABO blood type

The “+” factor dominates over the “- ” factor

Individuals that are Rh- receive one “-” allele
from each parent
 Mismatch between antigens can endanger a
pregnancy

If the mother is Rh- and father Rh+, the baby will have a heterozygous +/- genotype

However, the mother has a -/- genotype

During pregnancy, the uterus is an immunologically privileged site

Even though half the baby’s alleles are foreign, the mother’s immune system
will not attack the baby

However, the placenta pulls away from the endometrium112 during labor and
delivery

At that moment, the baby’s red blood cells encounter the mother’s immune
system

The immune system produces anti-Rh+ antibodies

If the mother carries another Rh+ baby, the mother’s anti-Rh+ antibodies will
attack the Rh+ molecule on the fetus’s red blood cells

This reaction can kill the fetus

Blood tests can determine the presence of anti-Rh+ antibodies

If they are present, the mother can receive an injection of anti-Rh antibodies
to prevent fetal death113
 Pleiotropy occurs when a single gene contributes to multiple, unrelated traits
 Mendel had identified examples of pleiotropy in his pea plant experiments
 He noticed that all plants with colored seed coats had colored flowers and leaf
petioles114
 At the same time, plants with white seed coats had white flowers and petioles
 Mendel did not understand this result
 One example of pleiotropy is albinism
 Pigment molecules produce color in humans

111
Check out Chaplin's 100-year-old pratfalls: http://charliechaplin2013
The endometrium is the inner membrane of the uterus.
113
One (contested) theory proposes that Henry VIII's wife Anne Boleyn (and maybe even his first wife Catherine of Aragon) was Rh-,
leading to a series of miscarriages and stillbirths—and, consequently, the English Reformation.
114
The petiole is the stalk attaching the leaf blade to the stem.
112
Science Power Guide | 40
The body requires certain enzymes to produce each pigment molecule

If the gene that codes for an enzyme fails, then the body does not produce any
pigment molecules
115
 Albinos suffer from a defective melanin -producing enzyme

This single gene mutation affects pigment production in all parts of the body
 Pleiotropy also controls the inheritance of the gene responsible for sickle cell anemia
 Polygenic inheritance occurs when multiple genes control a single phenotype
 The phenotype is often quantitative
 In other words, it appears as a range rather than
either/ or
 Traits controlled by polygenic inheritance include
height, weight, and skin color
 People are not either "short" or "tall"

Height appears in a range of continuous
variations
 Scientists have identified over 180 genes controlling
human height
 Environmental influences such as nutrition and
hormone levels can also affect height
 Polygenic inheritance also affects the genetic factors for
breast cancer
 A women has a higher risk for breast cancer if more
than one close relative has had breast cancer at a young
age116
 The two mutated genes BRCA1 and BRCA2 increase
the risk for breast and ovarian cancer
 However, a carrier of these genes will not necessarily develop cancer

Fewer than 10% of breast cancer cases arise from BRCA1 or BRCA2

Less than one percent of the general population carry either of these genes117118
 The combination of lifestyle factors and small genetic mutations are the
fundamental cause of most cancer cases
 William Bateson, Reginald Punnett and Edith Rebecca Saunders collaborated to study
linked genes
 They crossed purebred flower color and pollen grain shape in sweet peas
 Purple flowers (P) dominate over red flowers (p)
 Long grains (L) dominate round grains (l)
 As expected, the F1 generation consisted of purple flowers and long pollen grains
 However, the F2 generation produced strange results
119
 The phenotype ratio was 15.6:1:1.4:4.5 instead of 9:3:3:1
 Many more plants than expected developed purple flowers and long pollen grains

115
Recall that melanin is a natural pigment that gives color to hair, skin, and the iris.
USAD does not define “young”, but many cancer experts recommend that women who carry the BRCA1 or BRCA2 gene begin
clinical breast examinations at ages 25 to 35.
117
According to new estimates from the National Cancer Institute, 55-65% of BRCA1 and 45% of BRCA2 carriers will develop breast
cancer by age 70, compared to 12% of women in the general population. For more, check out http://tinyurl.com/gq6lc
118
It appears nature holds a grudge against Ashkenazi Jews, as members of this ethnic group have a higher prevalence of BRCA1 and
BRCA2 genes than people in the general population. Recall that Ashkenazi Jews are also prone to Tay-Sachs disease.
119
Remember that linked genes do not follow the law of independent assortment.
116
Science Power Guide | 41
Plants with red flowers and round pollen grains were three times more common
than Mendel’s laws had predicted
 Bateson, Punnett, and Saunders hypothesized that the flower color and pollen grain
alleles were linked
 Thomas Hunt Morgan proved the existence of linked genes
 Morgan did not accept Mendelian genetics and Darwin’s theory of natural selection
 He induced fruit flies to produce a new species in three ways

X-rays
Chemicals
Temperature
Morgan also raised fruit flies in the dark to see if their eyes would eventually disappear
 He noticed one morning that one male fly had white eyes instead of red
 He bred the white-eyed male with the red-eyed females

The F1 generation was entirely red-eyed

This result showed that red was
dominant to white
Phenotype
Number

However, the F2 generation did not
White eyed males
782
generate the expected 3:1 ratio between
Red-eyed males
1011
red and white
 Morgan theorized that the inheritance pattern
White-eyed females
0
of X chromosomes and autosomes differed
Red-eyed females
2459

He believed that white eye color in fruit
flies was linked to an X chromosome mutation

To verify this hypothesis, he crossed white-eyed males with the heterozygous F1
females

As Mendelian genetics predicted, some of the offspring were white-eyed
females
 Morgan’s studies confirmed the physical presence of alleles in chromosomes
 He won the 1933 Nobel Prize for his studies of mutations
 Morgan and his student Alfred Sturtevant argued that genes were arranged linearly on
chromosomes
 Linked genes are more likely to cross over if they are far apart
 Likewise, neighboring genes are unlikely to cross over
 The distance between two genes is known as a genetic map unit
 Sturtevant analyzed recombination data from different crosses to predict the relative
position of genes
 He successfully produced the first linkage map by studying Drosophila
 Numerous scientists built on Morgan and Sturtevant's studies to map the genes of
other species
 Reginald Punnett identified
linkage groups in pea plants
Temperature
Social Structure
 Many factors determine an
offspring’s sex
Environmental
 As in humans, fruit fly sex
Genetics
Chemicals
Factors that
chromosomes determine
influence an
an organism’s gender
embryo's gender
 Fruit flies will be female if they
have two X chromosomes

Science Power Guide | 42
Fruit flies will be male if they have only one X chromosome
120
 The Y chromosome does not affect the fruit fly’s sex
 In humans, the Y chromosome ensures that the baby will be male
 A gene known as SRY (sex reversal Y) controls human male traits
 This gene occurs on the Y chromosome
 Before sexual differentiation occurs, the embryo has a pair of gonads and both male
and female reproductive tracts
 These organs co-exist during the first two months of gestation
 The SRY turns on genes that signal the gonad to become testes rather than ovaries
 Without a Y chromosome, ovaries will develop
 Female sex hormones promote the development of the female reproductive system
while ignoring the male reproductive system
 In humans, several traits link to sex chromosomes
 Colorblindness is one such trait
 John Dalton first described this disorder in 1794
 The opsin gene occurs on numerous chromosomes

This gene and its variants allow the eye to detect different wavelengths of light

Mutation of this gene causes color blindness

This defective gene is found on the X chromosome
 The most common form of colorblindness is red-green

Individuals suffering from red-green colorblindness lack red, green, or both
pigment molecules needed for color vision

Colorblind females must inherit a faulty X chromosome from both parents

Colorblind males only need one faulty X chromosome
 Most of the Y chromosome’s genes control
sex determination and male fertility
Y chromosome
 The Y chromosome is significantly smaller
reveals male
Mitochondrial DNA
than the X chromosome
lineage
reveals female
 It contains fewer than 200 genes
lineage
 Traits determined by the Y-chromosome
will pass down through the male family
line
 Thus, the Y chromosome can be used to track male
lineage
 The pattern of inheritance in mitochondria and chloroplasts
do not follow Mendel’s laws
 Mitochondrial DNA is only inherited from the mother in
humans and most mammals
 Male mitochondrial DNA never enters the oocyte
during fertilization

Thus, mitochondrial DNA can be used to trace the
female lineage
 Punnett Squares
 Geneticists use Punnett squares to find the probability that
an offspring has a particular genotype
 The parent’s genotypes must be known
 First, draw a four-box square

120
Unlike humans, fruit flies can survive with an XXY set of sex chromosomes.
Science Power Guide | 43





Then, write the genotype of one parent at the top of the square
 Place one letter above each smaller box
Write the genotype of the second parent on the left side of the square
 Place one letter next to each smaller vertical box
Next, write the letter from the side of the square in each box
 To its right, write the letter from the top of the square
These boxes represent the probability of each genotype for four offspring
When conducting a dihybrid cross, use a 16-square box
 The remainder of the process is the same as for a monohybrid cross
 Genetic Testing
 Genetic counselors use a pedigree to identify genetic disease carriers
 This diagram allows them to determine the probability that children will inherit a
certain trait
 Doctors can perform chromosomal analysis on babies in utero121
122
 They perform most of these tests on mothers older than 35
 The odds of having a baby with a chromosomal abnormality increase dramatically
past this age
 Doctors perform chromosomal analysis through karyotyping
 This test involves removing fetal cells from the womb
121
This Latin phrase means “in the womb”.
Don’t worry, guys: your risk of fathering a child with chromosomal abnormality also increases with age. Gender equality FTW. –
Josephine
122
Science Power Guide | 44
There are two main ways to extract these cells
 In amniocentesis, doctors insert a long needle into the fluid compartment within
the fetal membrane
 In chorionic villus sampling (CVS), doctors remove a piece of fetal membrane

CVS is the more invasive method of the two
 Genetic testing can even occur before the embryo attaches to the uterine wall
 In vitro fertilization produces a zygote outside the body
 Doctors can isolate, remove, and test
one cell in an eight-cell embryo
Chromosomal analysis
 The other seven cells are then inserted
into the mother to develop normally123
 If genetic disorders are diagnosed early,
treatment can begin at birth
Possible Embryonic
 The discovery of fetal cells circulating in the
Genetic Tests
mother’s blood may lead to simpler and more
accurate genetic testing
 However, new genetic
technologies lead to ethical
DNA testing
Biochemical testing
and moral implications 124

123
This process is known as preimplantation genetic diagnosis (PGD, or embryo screening. If doctors detect an embryonic cell with a
disease-causing mutation, they can eliminate that cell and re-implant the normal cells in the mother’s uterus. For more information,
check out http://tinyurl.com/lrlyyvz.
124
We'll get into this when I discuss the Human Genome Project in Section III.
Science Power Guide | 45
MOLECULAR GENETICS
POWER PREVIEW
POWER NOTES
Early 20th century scientists made tremendous breakthroughs
in the study of genetics and cellular reproduction, bringing
together Mendelian genetics and Darwinian evolution
through modern evolutionary synthesis. In the second half of
the 20th century, scientists turned to studying DNA, RNA,
and protein synthesis. The Human Genome Project and
modern genetic techniques have had widespread implications
on our society, with applications in law enforcement,
agriculture, and the diagnosis and treatment of diseases.
According to the USAD outline, 17-18
questions (35%) should come from Section III.
18 questions (36%) come from Section III on
the USAD Science Practice Test.
Section III covers pgs. 50-81 of the USAD
Science Resource Guide.
The Modern Synthesis of Evolution and Genetics
 Charles Darwin’s Theory of Evolution
 Charles Darwin travelled to the Galapagos
Islands during his voyage aboard the H.M.S.
Beagle from 1831 to 1836.
 He observed many species on the islands
 He paid particular attention to 13
species of finches
 His travels and observations led him to develop
the theory of evolution
 Darwin’s theory contained three main parts
 Each generation produces more
offspring than the environment can
sustain
 All individuals in a species have different
heritable traits
 Only individuals with favorable traits
survive and reproduce
Excess offspring in each
generation
Natural selection of
favorable variations
Descent with
modification
Theory of
evolution

In 1859, Darwin published On the Origin of Species by Means of Natural Selection
 The scientific community greeted Darwin’s ideas with both acceptance and controversy
Science Power Guide | 46


At that time, few scientists understood how traits were passed from one generation
to the next125

Darwin could not explain the genetics behind evolution
Darwin also could not reconcile his theory with other ideas about inheritance

his ideas challenged three main theories
of the nineteenth century
Pangenesis

The 2000-year old Greek idea of
pangenesis still held weight
Blending

Blending inheritance continued to
Inheritance
serve as a hypothetical model
Lamarck's

Jean-Baptiste Lamarck
hypothesis
hypothesized that individuals inherit
traits their parents had acquired
during their lifetime126
 The Post-Darwin Era
 By the end of Darwin's lifetime, scientists were cracking
the mystery of inheritance
 Cytologist Walther Flemming described the process of
mitosis in 1878
 In the 1880s, developmental biologist August
Weismann linked meiosis, sexual reproduction, and
genetic variation
 Weismann hypothesized that crossing over during
meiosis fostered genetic variability and natural
selection
 He tested Lamarck’s theory of acquired traits
 In one experiment, Weismann removed the
tails127 of mice
 The resulting five generations still had tails
128
 Weismann concluded that somatic traits
could not be passed from parent to offspring
 Based on his experimental results, Weismann
proposed the germ plasm theory of heredity
 He posited that all germ cells are made of germ plasm

Germ plasm is the hereditary material that parents pass on to offspring
 Each organism has two distinct types of cells that separate early in embryonic
development

Somatic cells develop independently of germ cells129

Germ cells are part of the germ line130
125
Darwin published On the Origin of Species seven years before Mendel even published the results of his pea plant experiments.
Epigenetics has partly redeemed Lamarck's hypothesis, which he'd be glad to hear if he hadn't been dead for over a century.
127
Mice all over the world remember him as their very own Jack the Ripper.
128
Somatic simply means “of the body”. In this context it refers to externally expressed traits
129
But germ cells can give rise to somatic cells (remember stem cells in section 1?)
130
This is the sequence of cells that contain the genetic material to be passed down to offspring.
126
Science Power Guide | 47
Weismann’s radical theory rejected the three previous theories of pangenesis,
blending inheritance, and Lamarck’s theory of acquired inheritance131
 By the early 20th century, scientists realized that they would need to analyze the genetic
composition of entire populations to understand evolution
 Darwin recognized that natural selection acts on populations rather than individuals
132
 However, he could not study entire species
on the islands
 Many scientists felt that field observations were insufficient to study entire populations
 Instead, they favored rigorously controlled laboratory experiments
133
 These scientists included Thomas Morgan and Hugo De Vries
 Through his fruit fly studies, Morgan developed the chromosome theory of
inheritance
 Morgan had noticed that almost all traits mutated over time
134
 He experimentally proved the chromosome theory of inheritance

Modified, this theory formed the backbone of both Mendelian genetics and the
Darwinian idea of descent with modification
135
 Population geneticists made observations that reflected Mendel's findings
 Both Mendel and population geneticists experimented with heritable variations
 Mendel’s controlled experiment environment replicated the same conditions as a
non-evolving population136

Large population
Negligible
physical
mutations
No migration or
random events
Equal
reproductive
success
Random mating
Mendel’s ideal 3:1 phenotype and 1:2:1 genotype ratio will always hold true in this
type of population
Genotype Results
Genotype
 In 1902, Udny Yule observed that the sum of
Frequency
the two allele frequencies always equals 1
 This equality only holds true for a non100 purebred PP
0.25
evolving population
200 heterozygous Pp 0.5
 Take a situation where purebred
purple (PP) and white (pp) flowers are
100 purebred pp
0.25
crossed
 We then cross the F1 generation ( ∗ )
 First, we add the total number of alleles
Phenotype Results
100 ∗ 2  200 ∗ 1  400 P alleles

200 ∗ 1  100 ∗ 2  400 p alleles

300 purple
400
 The frequency of the P allele is
 0.5
100 white


131
The frequency of the p allele is
800
400
800
 0.5
Though Weismann’s theory has been modified over time, its “premise of the continuity of hereditary material is the basis of the
modern understanding of…physical inheritance”. (Encyclopedia Britannica)
132
The Beagle anchored in the Galapagos for just over a month, not enough time to chase down entire islands’ worth of finches.
133
Remember: Thomas Morgan proved gene linkage through fruit flies and Hugo de Vries “re-discovered” Mendel’s work in 1900.
134
USAD implies that Morgan developed this theory, but you may recall from section I that Walter Sutton and Theodor Boveri had first
identified chromosomes as the carriers of genetic material in 1902-03.
135
Remember that Mendel experimented on pea plants without any knowledge of Darwin’s theory of evolution.
136
These conditions are also identical to the conditions for Hardy-Weinberg equilibrium.
Science Power Guide | 48
We can then sum the two allele frequencies

0.5  0.5  1
 In 1903, William Castle theorized that a
population’s allele frequencies would remain
stable without natural selection
 This insight into evolving populations led to
the development of the Hardy-Weinberg
theorem
 The Hardy-Weinberg theorem states that a
population’s allele frequencies will not change
over time if equilibrium is reached
 Mathematician G.H. Hardy and German
physician Wilhelm Weinberg proposed this
theorem in 1908
 If any of these five conditions for
equilibrium are unmet, the population's
allele frequency will change over time
 The population undergoes microevolution
 For example, a population may have two alleles,
p and q, for a gene
 In a purebred p population,   0, and vice
versa

In other words, in a purebred
population, the entire population
expresses only the dominant or
recessive trait
 An population’s genotype frequency can be
represented by the equation   2 1
 This statement shows that the genotype is
the combination of one allele from each
parent
 The Hardy-Weinberg equation offers another
way to express genotype frequency
2
2
 This equation is written as   2    1137
Conditions for Hardy-Weinberg
equilibrium

Term
Large population
No new mutations
Random mating
No natural selection
Indicates

the frequency of the homozygous dominant phenotype

the frequency of the heterozygous dominant phenotype


No migration
the frequency of the homozygous recessive phenotype
 The Union of Genetics and Evolution
 By the 1930s and 1940s, scientists agreed that Mendelian genetics and evolution by natural
selection could coexist
 This agreement created the modern synthesis of evolution
 In the early 20th century, scientists filled in key gaps between evolution and genetics
137
Look familiar? The Hardy-Weinberg equation is identical to the equation Mendel used to find the genotype ratio of his pea plants.
Science Power Guide | 49
paleontology
embryology
Fields of major discovery in the
early 20th century
population genetics
biogeography
 British geneticist R.A. Fisher was trained in mathematics and biometry138
This expertise separated him from Mendel and Darwin
 Fisher applied statistics to analyze genetic variations in a population
 This research helped him write a groundbreaking 1918 paper explaining the inheritance
of quantitative traits
 American plant geneticist G. Ledyard Stebbins studied the formation of new plant species
139
 He discovered sympatric speciation
140
 In this process, new species form through either meiotic errors or polyploidy
 Many flowering plants undergo this method of speciation
 Nearly a century earlier, Darwin had had proposed the idea of allopatric speciation
 In this process, a new species develops when a population is reproductively isolated
 For example, different species of finches evolved on the isolated islands of the
Galapagos
 Theodosius Dobzhansky published Genetics and the Origin of Species in 1937.
 Dobzhansky worked as an evolutionary biologist under Thomas Morgan in the 1930s

Dobshansky helped
shape the modern
synthesis of evolution
defined evolution as a change in allele frequency within a
gene pool
suggested that mutation was the main force behind
evolution by natural selection
 Evolutionary biologist Ernst Mayr proposed the “biological species concept”

For Mayr, a species is a group of organisms that can naturally interbreed
Produce
both male
and female
offspring
Offspring
are viable
and fertile
Species
In The Evolutionary Synthesis, Mayr argued for the development of a modern synthesis
of evolution
 He also explained that variation and selection lead to evolutionary change in species
 Together, Fisher, Stebbins, Dobzhansky, and Mayr built on Darwin’s theory of evolution

138
Biometry refers to the application of statistics to biology.
This process involves the creation of new species from an ancestral species while both inhabit the same geographic region
140
Polyploid cells contain more than one pair of homologous chromosomes. Most cells are diploid, meaning they have just one pair of
homologous chromosomes.
139
Science Power Guide | 50






All individuals have different traits
 The variability in these traits come from mutation

Mutation leads to the creation of new genes, alleles, and phenotypes
During gamete formation, chromosomes segregate and sort independently
 This sorting produces new genetic combinations
Parents pass on their intact genes to their offspring
 This process occurs independently for each gene
Most generations will produce more offspring that can survive
 Individuals with traits suited to their environment will survive and reproduce
Microevolution will eventually lead to speciation, or macroevolution
Evolution can occur for numerous reasons141
Population
migration
Natural selection
Non-random
mating
Genetic Drift
Causes of
Evolution
Genetic Material
 The Discovery of DNA
 Despite the growing acceptance of Mendel’s work, most nineteenth-century scientists still
believed that genetic material passed from parent to offspring via proteins
 The nucleus contains many proteins
 The many possible combinations of 20 amino acids could account for many traits
th
th
 However, discoveries in the late 19 and early 20 centuries pointed to DNA as the
genetic material
 Swiss biochemist Friedrich Miescher discovered nuclein in 1869
 This molecule is a mixture of nucleic acids and chromosomal proteins
 Miescher was studying white blood cell proteins from the pus of infected human patients
 He noticed that a substance from the white blood cell nuclei had different chemical
properties than proteins did
 Enzymes that normally broke down proteins did not affect this substance
 He named this substance nuclein
 Between 1885 and 1901, German chemist Albrecht Kossel studied nuclein
 He discovered that nucleic acid consisted of four nitrogenous bases
Adenine
Cytosine
Nitrogenous Bases in
Nucleic Acid
Thymine
141
Guanine
Genetic drift occurs when a population’s allele frequency randomly changes
Science Power Guide | 51
Adenine and guanine have a double-ring structure
 Cytosine and thymine have a single-ring structure
 Kossel won the 1910 Nobel Prize for this discovery
 Russian-American biochemist Phoebus Levene discovered the monosaccharide
deoxyribose142
 Levene had worked closely with Kossel
 In 1919, Levene concluded that DNA is a one large polynucleotide that consists of a
long chain of mononucleotides
143
 It has three major components

Phosphate
Components of
DNA
Pentose sugar
Four nitrogenous
bases
Levene incorrectly believed the four nitrogenous bases appeared in equal proportions
 His faulty belief became known as the “tetranucleotide” hypothesis

It dominated scientific thinking until the 1950s

This hypothesis convinced scientists that DNA structure was too simple to hold
genetic material
 Studying Streptococcus pneumoniae bacterium led to further breakthroughs in discovering
the genetic material
 This bacterium caused most of the deaths during the Spanish influenza pandemic
 The pandemic began in 1918 and killed between 50 to 100 million people
worldwide
 Often, bacterial infections finished off influenza victims with weakened immune
systems
 Scientists knew that different strains of S. pneumoniae had different pneumoniacausing potencies144
 English microbiologist Frederick Griffith studied two strains of the bacterium
 The virulent S-strain contained a smooth polysaccharide capsule

This capsule protected the bacteria from the body’s immune system
 The non-virulent R-strain lacked this capsule
 Griffith inject mice with different strains and observed surprising results
 Griffith theorized that the S-strain transferred heat resistance to the R-strain

The R-strain then became virulent

In 1928, he named this transferred substance the “transforming principle”145

142
A nucleic acid composed of deoxyribose = deoxyribonucleic acid
“Pentose” refers to a sugar molecule with five carbon atoms. "Pent" means "five," and "-ose" refers to sugar. (Think "fructose,"
"sucrose," and my personal favorite, "glucose."
144
This is also known as a virulent property
145
To clear up any confusion, the “transforming principle” refers to DNA.
143
Science Power Guide | 52
 Michael Dawson and Richard
Sia of Columbia University
observed Griffith’s “transforming
principle” within test tubes146
 Using test tubes made the
process of isolating and
chemically analyzing the
principle simpler, better
controlled, and more reliable
 Scientists could then isolate
and chemically analyze the
transforming material
 Biochemist Oswald Avery of
Rockefeller University chemically
analyzed S. pneumoniae
 He concentrated on the
carbohydrate section of the
bacteria capsule
 The virulent S-strain had
this capsule, while the non-virulent R-strain did
not
 Avery believed that the carbohydrates caused
an immune response

The capsule’s polysaccharides trigged an
immune response

The patient’s body then produced
antibacterial antibodies
 In a 1933 work, Avery argued that the capsule
polysaccharides stimulated antibody production in
infected individuals

The polysaccharides essentially served as
antigens
 Avery aimed to identify the mysterious transforming
principle
 First, he sought to prove that the transforming
principle was biologically active
147
 He created an assay
to calculate the success
of transforming the R-strain into the S-strain

This procedure also determined if different
concentrations of the R-strain extract
would inhibit the cell’s growth
 When he observed this transformation, Avery made several important observations
 The transforming activity was very strong
 The level of activity decreased as he diluted the mixture of S-strain extract and nonvirulent bacteria
146
147
Saving those poor little mice from a slow and painful death, I suppose
An assay is a scientific procedure used to determine the level of a substance in a cell or other organic sample
Science Power Guide | 53
However, the transforming activity was still present even when only 0.01
microgram148 of substance was added to the R-strain
 Next, Avery needed to identify the chemical properties of the transforming principle
 Avery noticed that the transforming principle had the physical properties of a
nucleic acid
 In 1944, Avery and his colleagues Colin MacLeod and Maclyn McCarty described
the purified transforming principle as a “viscous and slightly cloudy solution”

They noticed that the principle “formed fibrous strands when mixed with
ethanol”149

The three scientists also observed that the transforming principle had high levels
of phosphorus

Phosphorus is found in DNA, but not proteins
 The transforming principle also absorbed light in the same manner as DNA
 Finally, Avery observed that enzymes that normally digested proteins, carbohydrates,
and RNA could not destroy the transforming principle
150
 DNAse , however, could break down the substance’s structure and activity
 The stronger the dosage of DNAse, the more dramatic the inactivation of the
transforming principle
 Avery concluded that DNA was the
genetic material
 The scientific did not receive this
conclusion happily

Most scientists still believed
that protein carried hereditary
material
 In 1952, Alfred Hershey and Martha
Chase studied the process by which
bacteriophages151 infected bacterium
 They sought to identify the molecule
that the bacteriophage transferred to
the bacterium
 Bacteriophages reproduce by
injecting their material into the
virus

The virus’s genetic material
embeds itself into the host
chromosome

When the bacteria reproduces,
the virus does so as well
 Hershey and Chase decided to use E.
coli as the target bacteria
32
 They injected radioactive
Pand 35S (phosphorus and sulfur) as tracers into the
bacteriophages

148
In other words, one hundred billionth of one gram
You can do this at home! Here’s the experiment: http://tinyurl.com/lk6nvxj
150
This is an enzyme that digests DNA
151
A bacteriophage is a virus that infects and replicates within bacteria
149
Science Power Guide | 54
If phosphate appeared in the bacterium, then the bacteriophage had transferred
DNA as its genetic material into E. coli
 If sulfur appeared, then the bacteriophage had transferred protein rather than DNA
 After infecting the E. coli bacteria, the two scientists forcibly separated the
bacteriophage and bacteria

They sheared off the virus from the protein with a high-speed kitchen
blender152153

Then, they separated the virus and bacteria through centrifugation154
 The sulfur remained in the bacteriophage
 The phosphorus entered the bacteria
 The experiment showed that DNA was the
genetic material transferred between the
bacteriophage and bacterium
 However, the scientific world did not realize the
importance of this finding until 1952
 Hershey finally received recognition when he
shared the 1969 Nobel Prize with two other
scientists155
 In the 1940s, Edwin Chargaff compared the DNA
composition of numerous prokaryotes and
eukaryotes
156
 He used paper chromatography
to organize
DNA molecules based on chemical properties
and size
 Then, Chargaff used enzymes to digest the DNA
of different organisms
 He noticed that different organisms had
different DNA compositions

The ratio of the four nucleotides was unequal157

Adenine
Thymine
Cytosine
Guanine
(% of DNA)
(% of DNA)
(% of DNA)
(% of DNA)
Humans
20
20
30
30
Dogs
22
22
28
28



152
153
154
155
However, Chargaff observed a consistent 1:1 ratio of adenine to thymine and
cytosine to guanine
He suggested that adenine paired with thymine and cytosine paired with guanine

This pairing is known as Chargaff’s rule
Chargaff’s discovery of base pairing was critical in the construction of the DNA
model
Note to self: do not try this experiment at home - Eric
Mmmm, bacteria smoothies.
In centrifugation, scientists spin a sample at high speeds to separate its components
Apparently the absence of a Y-chromosome disqualified Martha Chase from winning the Nobel Prize - Josephine
156
Scientists use chromatography to separate mixtures into their individual components. For more information, check out this excellent
link: http://tinyurl.com/yketr99
157
Remember that Levene proposed that DNA had an equal proportion of the four nucleotides in his “tetranucleotide” hypothesis
Science Power Guide | 55

James Watson and Francis Crick developed the
double helix model of DNA in 1953
 This model proposes that deoxyribose and
phosphate form the backbone of DNA strands
 These strands hold the complementary
nitrogenous bases together
 They hired scientist Rosalind Franklin to study
and improve X-ray crystallography
 In this technique, X-rays produce a “shadow”
image of a molecule

The image reveals the size, shape, and
spatial relationship of the molecule’s
internal structure
 Franklin successfully produced a 3-D doublestranded twisted ladder image

Sugar and phosphate seemed to form
the backbone of the DNA strands

Nitrogenous bases clustered near the
center of the two strands
 Watson and Crick also used a molecular
model building technique developed by
Nobel laureate158 Linus Pauling159
160
 Nature
published their paper on DNA
“[We have awarded Crick, Watson,
structure in 1953
and Wilkins the Nobel Prize] for
 That same year, the journal also
their discoveries concerning the
published Maurice Wilkins’ paper on
molecular structure of nucleic acid
X-ray crystallography
and its significance for information
 Wilkins was one of Franklin’s
transfer in living material.”
colleagues
- The Nobel Prize Committee
 Watson, Crick, and Wilkins shared the
1962 Nobel Prize in Physiology or
Medicine
 The Organization and Replication of DNA
 Typical prokaryotic DNA contains one million nucleotides within three thousand genes
 Prokaryotes only carry one copy of each gene
 They contain little non-essential genetic material
 In comparison, eukaryotic DNA is complex
161
 The DNA molecules are wrapped around histone
proteins162
 Exons are regions of the DNA molecule that actively code for proteins
158
Oh, this old thing? Pauling won the Nobel Prize 1954 for his work on chemical bonds. Going for a matched set, he won the Peace
Prize in 1963 for his efforts at opposing nuclear war.
159
He’s also the reason your mom made you take vitamins you probably didn’t need: http://tinyurl.com/lhm9re2
160
Nature is the People magazine of scientists: anyone who’s anyone is in it.
161
Histones are protein molecules that help condense DNA so it can fit inside the nucleus. Since histones are positively charged and
DNA is negatively charged, DNA can easily wrap around the histone.
162
Each human cell has 1.8 meters of DNA. If all of the DNA in a single human adult were unwound, it would stretch from the Earth to
the Sun and back 70 times.
Science Power Guide | 56
In contrast, regions of noncoding DNA are known as introns
 Introns and exons form messenger RNA molecules
 The genetic code consists of four letters

A



T
G
C
A group of three letters is a codon
Each codon codes for a unique amino acid
 tRNA transports this amino acid to ribosomes

Once in the ribosome, the amino acid joins proteins
 The letters of the genetic code can form 64 possible codons
 However, protein synthesis uses just 20 naturally occurring amino acids
 Multiple codons can code for a single amino acid

However, UGG only codes for trytophan
Three codons act as stop codons
UAA
UAG
UAG
These codons halt the process of protein synthesis
 AUG acts as a start codon
 This codon initiates the process of protein synthesis
 It also codes for the amino acid methionine
 Watson and Crick realized that the structure and function of DNA are closely related
 They suspected that DNA’s base pairing pattern provided clues to the process of
replicating genetic material
 In the 1950s, scientists proposed three possible models for DNA replication

Conservative replication
The new DNA molecule consists of two new strands
Semi-conservative replication
The new DNA molecule consists of one old and one new strand
Dispersive replication
The new DNA moelcule consists of a mix of old and new strands


Watson and Crick favored the
semiconservative model
 In this model, the original DNA
strands “unzip”

Then, each strand serves as a
template for the replication of a
new strand

The new DNA molecule then “zips”
itself back together

This process occurs every time
DNA replicates
Molecular biologists Matthew Meselson
and Franklin Stahl confirmed this model
Science Power Guide | 57
They studied the DNA replication process in detail
 Before DNA replication, they tagged the individual components of DNA with
nitrogen isotopes 14Nand 15N
15
N would be heavier than molecules that
 Molecules that synthesized with
14
synthesized with N
15

N has one more neutron than 14N
 Meselson and Stahl chose E. coli bacteria as their test subject

They grew E. coli near 15N for many generations

Eventually, all the nitrogen in the bacteria was in the form of 15N

The two scientists repeated this process with 14N

Then, they extracted the DNA from the bacteria and analyzed the DNA samples

The centrifuge stratified the DNA molecules by density

This stratification occurred every 20 minutes
15
 After every DNA replication, around 50% of the
N molecules had been transferred
into the new DNA molecule

This result confirmed the semi-conservative model of DNA replication
Many enzymes participate in DNA replication


The RNA
primase
attaches to the
end of the DNA
strand
Helicase unzips
the parent DNA
molecule
DNA primase
synthesizes
an RNA
primase
enzyme
DNa
fragments
replace the
RNA primase
DNA polymerase
synthesizes the
complementary
strand of DNA
DNA ligase
"rezips" the new
DNA fragment to
the parent
Helicase
Acts as an unzipper
Initiates DNA replication by unwinding the double helix
Forms a replication fork and bubble
Primase
Synthesizes new RNA primers
Atttaches these RNA primers to the replicating strands of DNA
DNA polymerase
Nuclease
DNA ligase
Serves as builder and proofreader
Continually adds complementary nucleotides to the daugher
DNA moelcule
Acts as an editor
Removes incorrect nucleotides
Acts as a zipper
Fills in holes in the new DNA molecule backbone with
phosphate
Science Power Guide | 58


Prokaryotes simultaneously produce new DNA strands on both sides of the parent strand
Eukaryotes have multiple DNA strands
 Thus, DNA replication can occur at multiple places simultaneously
 Mutations
 Mutations occur when DNA fails to replicate accurately
 They occur randomly during the replication process
 Environmental and metabolic factors can increase the probability of a mutation
 Mistakes and faulty repairs lead to damaged DNA and altered genes
 For example, if an erroneous amino acid is added, the protein may cease to function
 Most mutations are inconsequential
 They only affect the non-coding section of DNA
 Some mutations, however, can cause cancer or other diseases
 Other mutations offer benefits
 Certain individuals have a mutation that prevent HIV from binding to T lymphocytes

These people are resistant to AIDS
 Point mutations are the most common type of mutation
 This mutation occurs when a single nucleotide is affected in one of four ways
added

substituted
deleted
translocated
Scientists classify mutations based on their effect on the amino acid sequence: silent,
missense, nonsense, and frameshift163
Silent
One nucleotide
substitutes for
another
Missense
Nucleotide
substitution
changes the
coded amino acid
Nonsense
Frameshift
Nucleotide
substitution
produce a stop
codon
One nucleotide is
added or deleted
The codon codes
for the same
amino acid

An example of a silent mutation involves the amino acid
proline
 Four different codons code for proline
 This duplication means that, if the final letter of any
of the four possible codon changes, the codon will
still code for proline
All subsequent
codons are
affected
CCC
CCA
Proline
CCG
163
No one talks about the divergent. –Josephine
CCU
Science Power Guide | 59
DNA
 Ribonucleic Acid (RNA)
 Stanford biochemist Arthur Kornberg and his NYU mentor Severo Ochoa worked on RNA
 In 1959, they shared the Nobel Prize in Physiology or Medicine
164
 The prize acknowledged their work on RNA synthesis
 Kornberg’s son Roger won
the 2006 Nobel Prize in
Chemistry for his study of
Double stranded
Single stranded
transcription165
Deoxyribose
Ribose backbone
 RNA and DNA have several key
backbone
Smaller in size
differences
Larger in size
Has roles in many
Only role is to store
cellular functions
 RNA is a large molecule made
genetic info
up of nucleotides
 This molecule is known as a
polymer
 It comprises phosphate, ribose, and four nitrogenous bases
 It comes in three major types
RNA
rRNA
Stands for ribosomal RNA
Made in the nucloeolus
Combines with proteins to form ribosomes
mRNA
Stands for messenger RNA
Produced by DNA transcription
Carries genetic information to the ribosomses for translation
tRNA
Stands for transfer RNA
Carries a specific amino acid
Complements the nucleotides in mRNA
The eukaryotic nucleus produces all three types of RNA
 RNA can form two strands if necessary
 tRNA is especially likely to undergo this transformation
 RNA and DNA follow identical base-pairing rules
166
 Adenine pairs with uracil
 Cytosine pairs with guanine
 Hydrogen bonds connect nitrogenous bases in both DNA and RNA
 RNA stores information for protein synthesis
 In eukaryotes, DNA always remains in the nucleus
 It condenses during cell division
 DNA disperses during gene expression
 Transcription occurs when mRNA transfers the DNA genetic code to ribosomes167
 Eukaryotic and prokaryotic transcription are almost identical
 However, transcription occurs in the nucleus in eukaryotes

164
Kornberg was quite the accomplished scientist. He was the first to isolate DNA polymerase, the first to synthesize DNA in a test tube,
and the first to replicate virus DNA in vitro.
165
No daddy issues there, nope.—Josephine
166
Remember that in RNA, uracil replaces thymine.
167
Some viruses (including HIV) can transcribe RNA into DNA through reverse transcription
Science Power Guide | 60


Before transcription can occur, the DNA must unzip itself
 Only one strand of DNA serves as a template
Transcription involves three steps
Initiation
RNA polymerase binds the promoter region
Elongation
Nucleotides are added to the RNA strand
Termination
The RNA strand separates from the DNA template once it reaches a termination factor
In eukaryotes, RNA then undergoes further modification and maturation
 Two extra nucleotides known as a cap and a poly A tail attach to both ends of the
mRNA

The poly A tail is a long nucleotide consisting of adenine

Both facilitate mRNA transport and prevents degradation of the mRNA molecule
 RNA splicing removes sequences of introns

This process then stiches the exons portions together

Exons can combine in many ways to create a variety of mRNA transcripts and
proteins

Thus, cells can produce many more types of proteins than there are genes in the
human genome
 Finally, the RNA molecule detaches and moves into the cytoplasm
 The DNA structure returns to its normal double-stranded shape
 During protein synthesis, tRNA “translates” the genetic code into the language of proteins
 Translation occurs in three stages

Initiation
mRNA binds to a small ribosomal subunit
The first tRNA carrying methionine binds to the start codon on the
mRNA
A large ribosomal subunit binds to the smaller to create a P site
The tRNA can then "dock" at this site
Elongation
The next tRNA docks at the A site
The new amino acid forms a peptide bond with the first amino acid
The first tRNA exits the ribosome
The second tRNA moves from the A site to the P site, allowing the
next tRNA to enter
Termination
The translation process ends when a stop codon is encountered
The peptide chain detaches from the ribosome
The ribosomal complex disassembles
Science Power Guide | 61

Some proteins require modification before they are sent to their final destination
through the endomembrane system
 Certain amino acids may be removed
 Any of five types of molecules may be added
Lipids
Carbohydrates
Functional
groups
Disulfide
bridges
Metal ions
 During transcription, RNA splicing removes non-coding regions of RNA

These discarded pieces of RNA have many regulatory roles within the cell
 Ribozyme is involved in post-transcription RNA processing and protein synthesis

It can also splice itself

Thomas Cech and Sidney Altman discovered this molecule

They noticed that RNA could act as an enzyme or catalyst

Cech and Altman won the 1989 Nobel Prize for their studies of RNA’s
catalytic activities

The discovery of ribozyme led to the development of the RNA world hypothesis

According to this theory, RNA was the first genetic material

This theory also explains why RNA can perform multiple cellular tasks
 Micro RNA (miRNA) is a single-stranded discarded product of transcription
 Short interfering RNA (siRNA or RNAi) is produced when enzymes digest doublestranded RNA168

This molecule can regulate gene expression through several methods
Splicing newly
transcribed RNA
Blocking
translation
Enhancing RNA
degradation
Adding methyl
groups to DNA
to activate or
inactivate
transcription
Some forms of miRNA and siRNA are involved in both cancer formation and
defense against DNA and RNA viruses
Other nucleotide-related molecules also contribute to cellular metabolism
 Adenosine triphosphate (ATP) is the cell’s source of energy

ATP serves as a substrate for cyclic adenosine monophosphate (cyclic AMP)

This molecule is a second messenger in the signaling pathway
 Cells draw energy from guanosine triphosphate (GTP) during protein synthesis

GTP is also vital in the signal transduction pathway


168
siRNA molecules are as short as it gets for a RNA molecule, as they are usually only 20-25 base pairs in length.
Science Power Guide | 62
Modern Molecular Genetics
 Applications of Genetics
 Biotechnology uses molecular biology to manufacture useful products, improve the
human standard of living and to tackle environmental challenges
 Genetic breakthroughs have revolutionized many fields
Agriculture
Pharmaceutics
Medical practice
 One key development is the recombination of genes and DNA
This is a common process in nature
 In the process of conjugation, one bacterium transfers its DNA to another
bacterium

The host bacterium integrates the newly transferred DNA into its own genome
 Viruses can also inject their own genes into the host genome to survive and
reproduce
 However, scientists did not know how this process occurred until the early 1970s
After understanding DNA recombination, scientists next sought to manipulate genes
 Gene manipulation is known as genetic engineering
 Scientists first developed a method of cutting and pasting desired genes into a DNA
molecule
 They could then choose to mass produce the gene or to transform an organism
genetically
DNA recombination and gene manipulation requires the use of restriction enzymes
 All species possess these enzymes
 They cut DNA between nucleotides in a specific nucleotide pattern
 For example, Hind III cuts between two A’s in the pattern AAGCTT

This cut will produce a stand-alone A and the fragment AGCTT
In the 1950s, Swiss geneticist Werner Arber169 discovered restriction enzymes
 He isolated enzymes that could recognize specific DNA sequences
 However, he could only cut randomly through the DNA
Hamilton Smith of Johns Hopkins University discovered endonuclease R
 This enzyme can cut DNA at specific locations
 Arber, Smith, and Smith's co-researcher Daniel Nathans won the 1978 Nobel Prize in
Physiology or Medicine for their work on restriction enzymes





Werner
Arber
Hamilton
Smith
Daniel
Nathans
 Mass production of DNA
 Scientists had to learn to mass produce DNA before developing real-world applications of
recombination DNA technology
 The polymer chain reaction (PCR) is one such process
169
USAD typo here—Arber’s name is spelled “Werner Aber” on page 70 and 71 of the Science Resource Guide.
Science Power Guide | 63

Kary Mullis170 discovered this process in the 1980s

He won the 1993 Nobel Prize for this achievement
Denaturation
The starting reaction mixture includes genomic DNA, primers, and the four types of nucleotides
This mixture is heated to 95° C
The hydrogen bonds break, separating the two strands of DNA
Annealing
The mixture is cooled to between 50° and 60°C
The primers bind to their respective complementary sequences on the individual DNA strands
Extension (Elongation)
The mixture is heated to between 72° and 80°C (the optimal temperature for Taq polymerase)
The polymerase is added to the mixture
Primers initiate the continued addition of nucleotides to the DNA strands
PCR works because heat easily breaks the hydrogen bonds between two DNA
strands

Thus, the DNA polymerase must be able to withstand high heat levels
 Thomas Brock discovered the heat-resistant Taq polymerase in the 1960s

These enzymes can be found in thermophilic171 bacteria near hot springs
 PCR requires several ingredients

Double-stranded genomic DNA serves as the template

Chemically-synthesized primers complement the nucleotide sequence at each
end of the DNA strands

Nucleotides serve as building blocks and substrates for the polymerase
 PCR can be repeated many times

Repetition exponentially increases the total amount of DNA

Fewer than 30 cycles can produce over one million copies of DNA
 PCR has been used in diagnosis, research, and forensic science
 Scientists first used recombinant DNA technology to treat diabetes
 In ordinary human adults, the pancreas produces the hormone insulin
 Insulin regulates blood sugar levels

Blood sugar levels must stay relatively constant
 After a person eats, insulin helps transport the increased levels of blood glucose to
body cells

The cells then use glucose to manufacture ATP
 Diabetic patients cannot produce or process insulin
 These patients require frequent insulin injections

170
171
The second most famous person to graduate from my high school. (Do you need to ask who the first is?) - Josephine
The Greek word “thermophilic” loosely translates to “heat lover”. These bacteria thrive at temperatures between 113° and 252 °F.
Science Power Guide | 64
Unfortunately, insulin is difficult to synthesize either chemically or biochemically

In addition, human insulin is difficult to obtain172
Insulin from pigs, sheep, or cows can be
used to treat diabetic patients
Type I
Type II
 Their insulin amino acid sequence and
diabetes
diabetes
structure is similar to that of humans
 However, the body eventually builds
The pancreas
Body cells do
resistance to the injected insulin
cannot produce
not respond to

The immune system detects
insulin
insulin
differences between the animal and
human insulin

The body produces antibodies against the animal insulin

Insulin resistance greatly reduces the effectiveness of the insulin injections
Scientists can produce insulin with recombinant DNA technology
 A restriction enzyme cuts through the insulin gene

The gene is then injected into a bacterium plasmid

This process incorporates the gene into the host genome

When the bacterium reproduces, the insulin replicates as well
173
 This technology is highly cost-effective
Recombinant DNA technology has been used to treat several other diseases




Drug produced
Disease/Disorder treated
Growth hormone
Short stature
Erythropoietin
Anemia
Interferon
Cancer
 Humans share 99.9% of nucleotide sequences
3.1 million base pair differences make up the final 0.1%
These differences are caused by a single nucleotide polymorphism (SNP)
 A single point mutation changes just one nucleotide
 Restriction enzymes can recognize and cut these nucleotide differences

When a restriction enzyme cuts the DNA of two individuals, two different DNA
fragments form

The cut DNA fragment will match either the mother’s or the father’s genome

This DNA match is the basic principle of genetic variation and DNA
fingerprinting
 DNA fingerprinting has revolutionized the criminal justice system
 Its technical name is restriction fragment length polymorphism (RFLP)
 Law enforcement officers use RFLP to establish physical evidence
 This evidence can convict or exonerate a suspect
 This technique has wide applications


Paternity and
maternity
disputes
172
173
Identification of
individuals
Exoneration of
those wrongly
accused
Just thinking about an insulin donation gives me the shivers. Ugh, the needles!—Eric
Recall that in optimal conditions, bacteria can divide every twenty minutes.
Science Power Guide | 65
RFLP uses PCR, restriction enzyme digestion, and agarose gel electrophoresis
 PCR amplifies the DNA sample

Usually, very little DNA remains at a crime scene

Crime scene DNA can come from several sources

Hair
Saliva

Blood
Semen
Fabric
In order to analyze DNA fragments, restriction enzymes must first digest the DNA
fragments

Then, agarose gel electrophoresis organizes a person’s unique pattern of DNA
fragments

Different DNA fragments come from different individuals

The fragments migrate across a chamber filled with gel

This chamber has an electric field

The DNA fragments move towards the field's positive pole

DNA is an acid that donates hydrogen ions174

It will become negatively charged when placed in the electric field

The agarose gel acts as a molecular “sieve” that filters DNA fragments

This gel has a texture175 similar to Jell-O

Smaller pieces of DNA will move faster than larger fragments

Once the gel filters all the DNA, the suspect’s “ladder” pattern can be compared
with DNA recovered at a crime scene
DNA migrates towards
the positive pole of
the electric field
Agarose gel is placed in a
electric field with a buffer
The restrictiondigested DNA
fragments are placed
in a well
A ladder pattern
of DNA bands
form
 Genetic Modification
 Humans have attempted to genetically modify other species since first domesticating
animals 10,000 years ago
 We have selectively bred animals and plants for many reasons
To increase food
production

174
175
To produce
companion
animals
To provide
entertainment
To fight wars
Early geneticists practiced genetic modification as well
 Mendel sought special traits in his pea plants for commercial purposes
By definition, an acid is a substance that, when placed in water, increases the water’s concentration of hydrogen ions.
But sadly not taste.
Science Power Guide | 66
Darwin was an expert in artificial selection

He was a pigeon breeder
 Previously, selective breeding required natural
phenotypes and processes
 Genetic engineering rapidly expanded the scope of
selective breeding
 Genes could be isolated, identified, cloned, and
transferred between individuals and species
 Today, genetic engineering has several key applications
 Increase agriculture production
 Increase the production of rare drugs
 Aid in biomedical research
 Genetically modifying an organism is similar to
genetically modifying a gene
 However, in organisms, the desired gene must be
injected into the germ line or fertilized egg
 This injection ensures all of an offspring’s somatic
cells and gametes will express the desired gene

Methods of inserting
foreign genes into an
organism
Microinjecting the cloned DNA or transgene into the pronucleus
of the sperm or oocyte
Transferring the through a virus (retrovirus infection)
Injecting transformed embryoni stem cells into an early embryo
 Genetically modified organisms (GMOs) have many uses176
Increasing
agricultural
production
Producing drugs
and vaccines
Increasing
resistance to
pests and
disease
Enhancing
nutrient content
of crops
Reducing costs
of agriculture
and drug
production
Producing
environmentalresistant crops
 However, much debate surrounds the genetic modification of organisms
However, GMOs may pose risks to human health, other species, and the environment177
 Genetic modifications may cause allergic reactions in humans
 The long-term effects of these modifications on metabolism are still unknown
 New frontiers in genetics
 Epigenetics is the study of environmental and chemical factors that alter gene expression178
 These factors affect the inheritance of traits without altering the DNA sequence
 Scientists have long known that environment can influence individual traits
179
 Identical twins
share the same genes, but can have different traits

176
In the SmartArt below, “environmental-resistant” means resistant to environmental stressors such as drought.
Emphasis on the may: there is currently no scientifically accepted evidence against the use of GMOs.
178
The definition USAD gives in the text itself differs slightly from the glossary entry at the back of the Resource Guide. I’ve gone with
the latter here, as it appears to be in agreement with numerous online sources.
179
Or if you want to be fancy, monozygotic twins.
177
Science Power Guide | 67
Daughter cells can inherit environmentally modified genes180
 If the specific gene is found in a germ cell, future generations can also have the trait
 Chemicals influence our genes in two ways
 In DNA methylation, an extra methyl group CH  is added to the DNA backbone

This addition can either activate or inactivate the gene

If the methyl group binds to a nucleotide sequence, transcription my not occur

The methyl group can interfere with proteins

These proteins include the transcription factors that attach to the promoter
region of the gene
181
 Chemicals can also bind histones more tightly or loosely to DNA

Genes can be turned off or exposed to transcription factors and turned on

A genetic disease may occur if histones are modified in a coding region
 Cancer, diabetes, mental illnesses, and other diseases can be traced to epigenetic changes
182
 The mechanisms and factors of epigenetics are still little understood
Scientists made numerous genetic breakthroughs in the second half of the 20th century
 Stanford University scientists Paul Berg, Herbert Boyer, and Stanley Norman Cohen
identified, cloned, and sequenced many disease genes
 Many geneticists won Nobel Prizes
 Frederick Sanger won a second Nobel in 1980 for his work on DNA sequencing
The Human Genome Project (HGP) coordinated the efforts of individual geneticists to
sequence the entire human genome
 Scientists sought to map the location of all human genes on chromosomes
 They wanted to create linkage maps that showed all possible inherited traits
The National Institutes of Health and the Department of Energy were its primary funders
 James Watson was appointed the first director of the National Center for Human
Genome Research in 1989183
 The HGP eventually became a joint public-private competition
 Celera Genomics founder J. Craig Venter played a vital role in the project
New techniques such as RFLP, PCR, and synthetic bacterial and yeast chromosomes arose
during the project
 These techniques led to several re-adjustments of research goals and timelines
 The HGP was successfully completed ahead of schedule and below budget
Francis Collins presented a draft with 90% of the completed genome sequence in June 2000
 Collins had directed the sequencing of the cystic fibrosis gene in 1999
 He succeeded Watson as the head of the National Center for Human Genome Research
 Scientists published the entire human sequence in 2003
The HGP has offered scientists a better understanding of the human genome184







180
Turns out Lamarck may have been on to something after all.
According to “Molecular Signals of Epigenetic States”, a research paper by Robert Bonasio, et al., an epigenetic system should have the
potential to be passed from parents to offspring indefinitely, but should also be reversible. Scientists do not agree on whether histone
modification is a true epigenetic system, as “it is likely that relatively few of these modifications…will be self-perpetuating and inherited.”
182
If your curiosity has been piqued, check out this article: http://tinyurl.com/mp2ug54
183
This organization was created in 1989 as the National Institutes of Health’s component of the HGP.
184
USAD states that the Y chromosome is the smallest (pg. 78 of the Resource Guide), but the National Institutes of Health website
points to chromosome 21 as the smallest.
181
Science Power Guide | 68
The human genome contains about 3.1 billion nucleotides
Humans have about 22,5000 genes
Each gene contains about 3,000 base pairs
All humans carry about 99.9% of the same genome
Half of the human genome consists of repeating non‐coding sequences
The purposes of these sequences are still unknown
Coding regions make up only about 2% of our genome
Mutations occur more often in males
Human chromosomes have randomly distributed "gene rich" and "gene poor" regions
In contrast, most other species have genes that are approximately evenly distributed
Humans, flies, and roundworms share the majority of their gene families
However humans have an expanded gene family and a wider range of proteins
Alternative splicing of mRNA and post‐translational modification allow human intracellular molecules to
perform a variety of functions
Single nucleotide polymorphisms occurs at 1.4 million locations in the human genome
These areas can potentially be used to trace human evolution
They may also help us locate disease genes for new therapies
Chromosome 1 is the largest, with nearly 3,000 genes
The Y chromosome is the smallest, with about 200 genes
 HGP scientists believed the project had
Genetic
Employers and insurance companies should not use
many ethical, legal, and social
genomic information to discriminate in employment
Privacy
health care coverage
implications
Genomic
information should be used and interpreted
 They advocated genetic privacy
fairly
 The HGP project has also changed
how diseases are diagnosed and
The benefits of genomic research must be distributed
across all areas of society
treated185186
 This change affects the use of
pre-implementation and prenatal genomic diagnosis
 The HGP may be only the tip of the iceberg
 Functional genomics and proteomics are the current genetic frontiers
 Functional genomics seeks to understand how proteins interact with DNA
187
 Proteomics
seeks to understand how proteins interact with other proteins188
185
Over 2,000 genetic tests for human conditions have been developed as a result of the HGP.
For more information about the HGP’s impact on human life, check out http://tinyurl.com/mp8o3eo
187
Proteomics is a blend of the words “protein” and “genome”.
188
Current research in this field involves mimicking a missing protein or altering the shape of a defective one. Scientists hope to use this
knowledge to develop “personalized” forms of cancer drugs (among other diseases) that will be more effective and have fewer side effects.
186
Science Power Guide | 69
CONCLUSION
POWER PREVIEW
POWER NOTES
The field of genetics stretches from Greek philosophers’ first
attempts at analyzing inheritance two thousand years ago to
Mendel’s studies of pea plants, from the modern evolutionary
synthesis to the Human Genome Project.
 According to the USAD outline, 0
questions should come from the
Conclusion.
 0 questions come from the Conclusion on
the USAD Science Practice Test.
 The Conclusion covers pg. 81 of the USAD
Science Resource Guide
The USAD Science Guide, in One Page
 Another Brief History of Genetics
 Scientists first hypothesized about the inheritance of traits over two thousand years ago
th
 However, the scientific study of inheritance did not begin until the early 20 century
 Scientists called this study “genetics”
 Modern biology builds upon Mendelian inheritance and Darwinian evolution
 This era began with the discovery of DNA’s structure and function
 The Human Genome Project, completed in 2003, is one of many recent genetic
accomplishments
 For the first time, scientists understood that all human diseases have genetic roots
 Scientists hope that the completed project will lead to treatments for many diseases
 Genetics in a Nutshell
 Section I reviews the structure and processes of cells
 It details the life cycles of both single cell and multicellular organisms
 It also covers the stages of cell division and gamete production in sexually reproducing
species
 This section ends with a discussion of cell cycle regulation and malfunction
 Section II breaks down Mendel’s studies and three laws of inheritance
 Mutations, gene location, and differences in gene regulation can affect Mendelian
inheritance
 Simple trait inheritance is only one of many possible patterns of inheritance
 Scientists study these patterns to broaden their understanding of genetic diseases

They need to understand the origins of these diseases before developing
effective treatments
 Section III analyzes modern trends in the study of genetics
 It details the connection between genetics and evolution
 Genetics provide much of the evidence for evolution
 This section also explains historically important experiments that analyzed the physical
nature of genes and inheritance
 Genetics today has revolutionized agriculture, disease treatment and diagnosis, and the
criminal justice system
 However, modern applications of genetics carry a wide range of ethical, social, and
legal implications
Science Power Guide | 70
POWER LISTS
All numbers in parentheses refer to the page numbers of the USAD Resource Guide189 where you can find the
original context of the defined term.
PEOPLE—GENETICISTS







189
Albrecht Kossel (54)
-
German chemist
-
Identified the four nitrogenous bases of DNA
-
Won the 1910 Nobel Prize in Physiology or Medicine
-
Worked at the Cold Spring Harbor Laboratory
-
Determined that viruses pass DNA, not proteins, to their
host
-
Won the 1969 Nobel Prize in Physiology or Medicine
-
Thomas Morgan’s student
-
Developed the first gene linkage map
-
Theorized that genes are arranged linearly on
chromosomes
-
Observed the distance between two linked genes is directly
proportional to the probability of crossing over between
them
Archibald Edward Garrod (8,
38)
-
British physician
-
Discovered the first genetic disease (alkaptonuria) in 1902
Aristotle (6)
-
Greek philosopher
-
Published History of Animals and Generation of Animals
-
Hypothesized that an offspring was the product of the
parents’ co-mingled blood
-
Biochemist at Stanford University
-
Won the 1959 Nobel Prize in Physiology or Medicine
-
Studied DNA and RNA synthesis
-
German developmental biologist
-
First scientist to link meiosis, sexual reproduction, and
genetic variation
-
Experimented on mice
-
Disproved pangenesis, blending inheritance, and
Lamarckian inheritance
-
Developed the germ plasm theory of heredity
-
Theorized that crossing over during meiosis led to genetic
variation
Alfred Hershey (57)
Alfred Sturtevant (8, 46, 78)
Arthur Kornberg (65)
August Weismann (50, 51)
Some editions may vary, particularly those offered to schools as digital subscriptions.
Science Power Guide | 71









Carl Erich Correns (7, 37)
Colin MacLeod (57)
Daniel Nathans (71)
Edith Rebecca Saunders (45)
Edmund Wilson (8)
Edouard van Beneden (7)
Eduard Strasburger (7)
Edwin Chargaff (58)
Erich von TschermakSeysenegg (7, 37)
-
German botanist and geneticist
-
Investigated effect of extra-chromosomal factors on
physical traits
-
Studied garden peas
-
Published a 1900 paper referencing Mendel’s law of
segregation and independent assortment
-
Oswald Avery’s colleague
-
Demonstrated that Griffith’s “transforming principle” was
DNA, not protein
-
Worked with Hamilton Smith on restriction enzyme
research
-
Shared the 1978 Nobel Prize in Physiology or Medicine
with Werner Arber and Hamilton Smith
-
British botanist and plant geneticist
-
Conducted dihybrid crosses of sweet peas with William
Bateson and Reginald Punnett
-
Discovered linked genes
-
American embryologist
-
Discovered the difference between male and female sex
chromosomes
-
Observed that sex-linked traits do not follow Mendel’s law
of independent assortment
-
Belgian scientist
-
Developed a technique for staining a cell’s nucleus and
chromosomes
-
Polish scientist
-
Developed a technique for staining a cell’s nucleus and
chromosomes
-
Compared DNA from different organisms
-
Used paper chromatography and enzymes to analyze the
nucleotide composition of DNA molecules
-
Discredited Levene’s “tetranucleotide” hypothesis
-
Developed Chargaff’s rule of base pairing
-
Austrian scientist
-
Grandson of Mendel’s biology professor at the University
of Vienna
-
Confirmed Mendel’s 3:1 phenotype ratio through plant
breeding experiments
-
Published his research in June 1900
Science Power Guide | 72






Ernst Mayr (54)
Estella Elinor Carothers (9)
Francis Collins (79)
Francis Crick (58-60)
Franklin Stahl (61)
Frederick Griffith (56)
-
Evolutionary biologist
-
Proposed the “biological species concept”
-
Published The Evolutionary Synthesis
-
First scientist to present cytological evidence for the
independent assortment of chromosomes
-
Observed cell division in grasshopper testes
-
Led the 1999 sequencing of the cystic fibrosis gene
-
Succeeded James Watson as director of the Human
Genome Project
-
Developed the double helix DNA model and semiconservative model of DNA replication
-
Shared the 1962 Nobel Prize in Physiology or Medicine
with Watson and Wilkins
-
Worked at the same research institute as Wilkins and
Franklin
-
Molecular biologist
-
Confirmed the semiconservative model of DNA replication
-
English microbiologist
-
Studied the smooth S- and rough R-strain of S.
Pneumoniae
-
Believed that the transfer of a “transforming principle”
allowed the R-strain to acquire a heat-resistant substance
from the S-strain

Frederick Sanger (78)
-
Won his 2nd Nobel Prize (in Chemistry) in 1980 for
developing DNA sequencing techniques

Friedrich Miescher (54)
-
Swiss biochemist
-
Discovered nucleic acid in 1869
-
British mathematician
-
One of two developers of the Hardy-Weinberg theorem
-
Austrian monk and founder of genetics
-
Grew up on a farm
-
Studied at the University of Vienna with Tschermak’s
grandfather
-
Failed the teacher certification examination twice
-
Became an ordained minister at a Brno monastery in 1847
-
Observed 30,000 pea plants from 1856 to 1864
-
Developed the three laws of genetics
-
Published Experiments on Plant Hybridization in 1868


G.H. Hardy (52)
Gregor Mendel (5, 6, 28, 30,
33, 35, 48, 80, 82)
Science Power Guide | 73









Hamilton Smith (71)
Hippocrates (6)
Hugo de Vries (7, 37)
J.B.S. Haldane (9)
James Watson (58-60, 79)
Joseph Kolreuter (6)
Karl Landsteiner (42)
Kary Mullis (73)
Linus Pauling (59)
-
Researcher at Johns Hopkins University
-
Discovered endonuclease R
-
Shared the 1978 Nobel Prize in Physiology or Medicine
with Daniel Nathans and Werner Arber
-
Greek philosopher
-
Developed the theory of pangenesis
-
Dutch botanist and geneticist
-
Studied the role of mutations in evolution
-
Developed a plant-breeding program similar to Mendel’s
-
Acknowledged Mendel’s prior genetics research in a 1900
paper
-
British evolutionary biologist
-
Co-founder of population genetics and modern
evolutionary synthesis
-
Developed the double helix DNA model and semiconservative model of DNA replication
-
Shared the 1962 Nobel Prize in Physiology or Medicine
with Wilkins and Crick
-
Worked at the same research institute as Wilkins and
Franklin
-
First head of the National Center for Human Genome
Research
-
Directed the Human Genome Project
-
First scientist to study genetic crosses
-
Used tobacco plants to support Hippocrates’s idea of
pangenesis in the 1760s
-
Austrian scientist
-
Studied the agglutination patterns of different blood types
-
Discovered the ABO blood typing system
-
Won the 1930 Nobel Prize in Physiology or Medicine
-
Developed the polymerase chain reaction process in the
1980s
-
Won the 1993 Nobel Prize in Chemistry
-
Won the 1954 Nobel Prize in Chemistry for his “research
into the nature of the chemical bond and its application
to the elucidation of the structure of complex substances”
-
Developed a molecular model building technique used by
Watson and Crick
Science Power Guide | 74









Maclyn McCarty (57)
Martha Chase (57)
Matthew Meselson (61)
Maurice Wilkins (60)
Michael Dawson (56)
Nettie Stevens (8)
Oswald Avery (56)
Phoebus Levene (54)
Plato (6)
-
Oswald Avery’s colleague
-
Demonstrated that Griffith’s “transforming principle” was
DNA, not protein
-
Worked at the Cold Spring Harbor Laboratory
-
Alfred Hershey’s assistant
-
Determined that viruses pass DNA, not proteins, to their
host
-
Molecular biologist
-
Confirmed the semiconservative model of DNA replication
-
Rosalind Franklin’s colleague
-
Published a 1953 paper in Nature with Franklin’s X-ray
data
-
Shared the 1962 Nobel Prize in Physiology or Medicine
with Watson and Crick
-
Scientist at Columbia University
-
Replicated Frederick Griffith’s experiment in a test tube
-
American embryologist
-
Discovered the difference between male and female sex
chromosomes
-
Scientist at Rockefeller University
-
Studied the chemical composition of S. Pneumoniae
-
Theorized that the polysaccharides in the bacteria’s
capsule stimulated antibody production in infected
patients
-
Chemically analyzed the “transforming principle” and
confirmed that it was DNA
-
Russian-American biochemist
-
Worked with Albrecht Kossel
-
Identified deoxyribose as a part of DNA
-
Concluded that DNA is a long-chain polynucleotide
consisting of sugar, phosphate, and nitrogenous bases
-
Proposed the erroneous “tetranucleotide” hypothesis
-
Greek philosopher
-
Theorized about reproduction, embryonic development,
and heredity
Science Power Guide | 75








Reginald Punnett (8, 40, 45)
Richard Sia (56)
Roger Kornberg (65)
Ronald A. Fisher (9, 53)
Rosalind Franklin (58, 59)
Severo Ochoa (65)
Sewall Wright (9)
Sidney Altman (69)
-
British geneticist
-
Conducted dihybrid crosses of sweet peas with William
Bateson and Edith Rebecca Saunders
-
Discovered linked genes
-
Creator of the Punnett square
-
Scientist at Columbia University
-
Replicated Frederick Griffith’s experiment in a test tube
-
Researcher at Stanford University
-
Arthur Kornberg’s son
-
Won a Nobel Prize in Chemistry
-
Discovered DNA transcription
-
British statistician and geneticist
-
Co-founder of population genetics and modern
evolutionary synthesis
-
Controversially supported eugenics
-
Trained in biometry
-
Statistically analyzed genetic variations within a
population
-
Published a revolutionary 1918 paper on the inheritance
of quantitative traits
-
Maurice Wilkins’s colleague
-
Worked at the same research institute as Watson and
Crick
-
Studied and refined X-ray crystallography
-
Produced images of the DNA molecule that Crick and
Watson used in their research
-
Researcher at New York University
-
Won the 1959 Nobel Prize in Physiology or Medicine
-
Studied DNA and RNA synthesis
-
Arthur Kornberg’s mentor
-
American geneticist
-
Co-founder of population genetics and modern
evolutionary synthesis
-
Studied the enzymatic and catalytic activities of RNA
-
Developed the RNA world hypothesis
-
Shared the 1989 Nobel Prize in Chemistry with Thomas
Cech
Science Power Guide | 76



Socrates (6)
Theodor Boveri (7)
Theodosius Dobzhansky (54)
-
Greek philosopher
-
Theorized about reproduction, embryonic development,
and heredity
-
German scientist
-
Observed the segregation of chromosomes during
meiosis
-
Theorized that chromosomes transferred genetic material
between generations
-
Evolutionary biologist
-
Worked with Morgan in the 1930s
-
Wrote Genetics and the Origin of Species
-
Defined evolution as “a change in allele frequency within a
gene pool”
-
Theorized mutation was the driving force behind
evolution

Thomas Brock (73)
-
Discovered Taq polymerase in the 1960s

Thomas Cech (69)
-
Studied the enzymatic and catalytic activities of RNA
developed the RNA world hypothesis
-
Shared the 1989 Nobel Prize in Chemistry with Sidney
Altman
-
Confirmed the existence of linked genes
-
Demonstrated that linked genes existed on the sex
chromosome
-
Studied and experimented with fruit flies
-
Induced fruit flies to produce a new species through the
use of X-rays, temperature, and chemicals
-
Developed the first gene linkage map
-
Theorized that genes are linearly arranged on
chromosomes
-
Won the 1933 Nobel Prize in Physiology or Medicine
-
American scientist
-
Observed the segregation of chromosomes during
meiosis
-
Theorized that chromosomes transferred genetic material
between generations
-
German scientist
-
Developed a technique for staining a cell’s nucleus and
chromosomes
-
First scientist to use the word “mitosis” to describe cell
division



Thomas Hunt Morgan (8, 9,
37, 45, 46, 51, 54, 78)
Walter Sutton (7)
Walther Flemming (7, 50)
Science Power Guide | 77




Werner Aber (71, 72)
Wilhelm Weinberg (52)
William Bateson (8, 44, 45)
William Castle (52)
-
Swiss geneticist
-
Isolated enzymes that could “read” specific DNA
sequences
-
Shared the 1978 Nobel Prize in Physiology or Medicine
with Daniel Nathans and Hamilton Smith
-
German physician
-
One of two developers of the Hardy-Weinberg theorem
-
British geneticist
-
Conducted dihybrid crosses of sweet peas with Edith
Rebecca Saunders and Reginald Punnett
-
Discovered linked genes
-
Translated Mendel’s works into English
-
American geneticist
-
Theorized that allele frequencies would remain constant if
no natural selection occurred
-
Thick layer of polysaccharides
-
Attaches to the cell wall of bacteria
-
Traps nutrients
-
Defends bacteria from host immune system
-
Barrier found outside the plasma membrane
-
Protects the cell from environmental changes
-
Made of peptidoglycan (prokaryotes) or cellulose (plants)
-
Found in plants and certain protists
-
Acts as a lysosome in single-celled protists
-
Maintains turgor pressure on cell walls
-
Stores pigments and wastes
-
Maintains proper water and salt levels within the cell
CELL STRUCTURES



Capsule (13, 56)
Cell wall (9, 11, 13, 18, 19,
20, 22)
Central vacuole (16, 18)

Centriole (17, 18)
-
Anchors the spindle fibers during cell division

Centromere (18, 20-22, 24,
25)
-
Sister chromatids join together here
-
Spindle fibers also attach here during cell division
Centrosome (17-19, 21, 22)
-
Functions as a microtubule organizing center
-
Consists of many centrioles

Science Power Guide | 78






Chloroplast (17, 29, 47, 49)
-
Found only in plants and photosynthetic protists
-
Transforms solar energy into ATP through photosynthesis
-
Contains chlorophyll pigments
-
Can self-replicate
-
Contains its own DNA and ribosomes
-
Surrounded by a double layer of membranes
-
Believed to have descended from symbiotic prokaryotes
living within eukaryotic cells
Chromosome (7, 8, 9, 11, 13,
15, 16, 18- 29, 31-33, 36, 37,
39, 45-47, 49- 51, 54, 57, 60,
61, 76-80)
-
Molecule consisting of DNA, RNA, and proteins
-
Found within the nucleus
-
Stores genetic information
-
Always found in pairs (see homologous chromosomes)
Cilia (17)
-
Small projections on the plasma membrane
-
Consist of microtubule bundles
-
Assist in cell locomotion and surface adhesion
-
Region of the cell surface
-
LDL molecule clusters near this region before entering the
cell through endocytosis
-
Aqueous medium that houses all subcellular organelles
-
Stores minerals, salts, and vitamins
-
Location of most cellular activities
-
System of fibers
-
Acts as the cell’s muscle and skeleton
-
Responsible for cell movement, organelle organization,
and cytokinesis
-
Consists of microtubules, intermediate filaments, and
microfilaments
Coated pit (42)
Cytoplasm (12-20, 22, 24,
25, 67, 68, 80)
Cytoskeleton (15, 17, 67)

Cytosol (12, 14, 16)
-
Fluid portion of the cytoplasm

Endomembrane system (16,
68)
-
Responsible for modifying and specializing non-cytosolic
proteins
-
Includes the nuclear envelope, rough and smooth ER,
Golgi apparatus, and transport vesicles
-
Whip-like structures
-
Allow the cell to move in aqueous environments
-
Contain one or two large tails
-
Found in sperm cells
-
Consist of microtubule bundles

Flagella (11, 13, 17)
Science Power Guide | 79









Golgi apparatus (16, 20, 68)
-
Group of membranous sacs
-
Modifies, packages, and ships proteins to their final
destination
-
Receives proteins from the rough ER
-
Also known as the Golgi complex or body
Intermediate filament (15,
17)
-
Stabilizes and maintains organelle position
-
Structure resembles the steel cables of suspension bridges
Kinetochore (21, 22, 24, 25)
-
Protein structure
-
Only appears during mitosis and meiosis
-
Spindle fibers attach here to pull sister chromatids apart
-
Protein molecule
-
Found on the cell surface
-
Recognizes and internalizes LDL molecules
-
Mutations in the LDL receptor gene prevent this protein
from binding and clustering LDL
-
Digests food particles through endocytosis
-
Eliminates aged and worn cellular structures through
autophagy
-
Only found in animal cells
-
Thinnest of the three cytoskeletal elements
-
Plays a key role in many cellular procedures
-
Largest of three cytoskeletal elements
-
Provides intracellular support
-
Transports molecules throughout the cell
-
Acts as a spindle fiber during cell division
-
Forms the “backbone” of cilia and flagella
-
Attached to centrosomes in animal cells
-
Controls energy production
-
Used to trace the female lineage
-
Male mitochondrial DNA is located in the middle of the
sperm and destroyed during fertilization
-
Found only in animal cells
-
Produces ATP molecules through cellular respiration
-
Can self-replicate
-
Contains its own DNA and ribosomes
-
Surrounded by a double-layer of membranes
-
Believed to have descended from symbiotic prokaryotes
living within eukaryotic cells
LDL receptor (42, 64)
Lysosome (16, 20)
Microfilament (15, 17, 22)
Microtubule (15, 17-19, 21,
22, 24)
Mitochondrial DNA (48)
Mitochondrion (17, 29, 47,
48)
Science Power Guide | 80









190
Nucleoid (10, 12, 13, 32, 60)
-
Stores prokaryotic genetic material
-
Houses a single circular DNA molecule
-
Round, granular structure
-
Found in the nucleus
-
Consists of protein and RNA
-
Produces ribosomal RNA
Nucleus (7, 9-21, 24, 25, 28,
29, 31, 32, 47-49, 54, 60, 6568, 77, 80)
-
Stores genetic information in eukaryotic cells
-
Sends mRNA to ribosomes
-
Location of the nucleolus
Pili (13)
-
Appendages that surround some bacteria
-
Shorter and finer than flagella
-
Allow surface adhesion
-
Also known as fimbriae
-
Semi-permeable barrier surrounding the cell
-
Consists of a double layer of phospholipids
-
Has protein channels that allow molecules to enter and
exit the cell
-
Isolated DNA molecule found only in prokaryotes
-
Can self-replicate
-
Can carry beneficial foreign genes
-
Circular in shape
-
Double-stranded
-
Complex of ribosomal RNA and around 36190 proteins
-
Serves as the cell’s protein “factory”
-
Is either cytosolic (free-floating in the cytosol) or attached
to the rough ER
-
Acronym for rough endoplasmic reticulum
-
The first destination for non-cytosolic proteins after
synthesis
-
Rugged surface texture due to presence of ribosomes
-
Acronym for smooth endoplasmic reticulum
-
Contains no ribosomes
-
Synthesizes lipids, steroids, and carbohydrates
-
Detoxifies poisons that enter the cell
Nucleolus (16, 20, 22, 24, 65)
Plasma membrane (10, 1317, 19, 29, 42)
Plasmid (13, 75)
Ribosome (13, 14, 16, 17, 60,
61, 65, 67-69, 80)
Rough ER (16)
Smooth ER (16)
USAD says that ribosomes “are composed of more than seventy different types of protein” on page 16 of the Resource Guide.
Science Power Guide | 81

Vesicle (12, 16, 21, 22)
-
“Pinched off” piece of plasma membrane
-
Stores and transports proteins
-
Produced by the endomembrane system
DATES

1794 (47)
-
John Dalton describes colorblindness

1831 (50)
-
Charles Darwin embarks on his voyage around the world
on the H.M.S. Beagle

1836 (50)
-
Charles Darwin concludes his voyage around the world on
the H.M.S. Beagle

1854 (30, 31)
-
Gregor Mendel begins his pea plant experiments

1859 (50)
-
Charles Darwin publishes On the Origin of Species by
Means of Natural Selection

1865 (31)
-
Gregor Mendel concludes his pea plant experiments

1866 (7, 36, 48)
-
Gregor Mendel publishes Experiments on Plant
Hybridization

1868 (37, 42)
-
Gregor Mendel becomes prelate of the Brno monastery
-
Karl Landsteiner is born

1869 (54, 65)
-
Friedrich Miescher discovers nucleic acid

1878 (7, 50)
-
Walther Flemming observes and describes the behavior of
chromosomes during mitosis

1884 (37)
-
Gregor Mendel dies

1890 (37)
-
Hugo de Vries begins to study mutation and plant
breeding

1900 (7, 28, 37, 44, 48, 51,
53)
-
Hugo de Vries, Carl Correns, and Erich Tschermak publish
research papers confirming Mendel’s laws

1902 (7, 9, 38, 52)
-
Udny Yule discovers that the allele frequencies in a
population will always add to one
-
Archibald Garrod describes alkaptonuria, the first disease
linked to genes
-
Walter Sutton and Theodor Boveri develop the
chromosome theory of inheritance
-
William Castle theorizes that allele frequencies would
remain constant if no natural selection occurred

1903 (52)
Science Power Guide | 82


1910 (45, 54)
1918 (9, 53, 55)
-
Sex chromosomes are discovered191
-
Albrecht Kossel wins the Nobel Prize in Chemistry
-
R.A. Fisher publishes a paper on the inheritance of
quantitative traits
-
World War I ends
-
Spanish influenza pandemic begins

1928 (56)
-
Frederick Griffith describes a substance that can pass traits
from one organism to another as a “transforming
principle”

1930s and 1940s (53)
-
Scientists seek to unify evolution and genetics

1933 (46, 56)
-
Oswald Avery studies the chemical composition of
Streptococcus pneumoniae

1943 (42, 43)
-
Barry/Chaplin case is brought to court

1950s (10, 70, 71)
-
Stanley Miller and Harold Urey show that inorganic
molecules could form organic molecules under early Earth
conditions
-
Werner Arber isolates restriction enzymes

1952 (57, 58)
-
Alfred Hershey and Martha Chase determine that viruses
transfer DNA, not protein, to their hosts

1953 (58, 60, 65)
-
James Watson and Francis Crick develop the double helix
DNA model

1958 (61)
-
Matthew Meselson and Franklin Stahl experimentally
prove the semiconservative model of DNA replication

1960s (73)
-
Thomas Brock discovers Taq polymerase in thermophilic
bacteria

1962 (60)
-
Francis Crick, James Watson, and Maurice Wilkins win the
Nobel Prize for Physiology or Medicine

1969 (58)
-
Alfred Hershey and two other scientists win the Nobel
Prize in Physiology or Medicine

1970 (41, 71)
-
The Southwest Medical Center admits 14-year-old J.D.,
who is suffering from high blood cholesterol levels

1970s (71)
-
Scientists discover the mechanisms behind bacterial
conjugation192

1980s (73)
-
Kary Mullis develops the polymer chain reaction process
191
The article “Sex Chromosomes and Sex Determination” by Ilona Miko asserts that Edmund Wilson first linked sex determination to
the X chromosome (discovered by C.E. McClung in 1901) in 1905. See http://tinyurl.com/kqlf3s7.
192
Recall that bacteria can transfer genetic material through direct cell-to-cell contact or a bridge-like connection. This process is known
as conjugation.
Science Power Guide | 83

1984 (43)
-
Courtrooms first use DNA fingerprinting

1989 (70, 79)
-
James Watson heads the National Center for Human
Genome Research
-
Sidney Altman and Thomas Cech share the Nobel Prize in
Chemistry

1999 (79)
-
Francis Watson leads the sequencing of the cystic fibrosis
gene

2000 (79)
-
Scientists reveal a rough draft of the Human Genome
Project

2003 (38, 79, 80)
-
Scientists complete the Human Genome Project
NUMBERS

0 (45)
-
Number of white-eyed female fruit fly offspring when
Morgan crossed a red-eyed F1 male and red-eyed F1
female

3 (37)
-
Maximum number of traits Mendel crossed at the same
time

4 (11, 12, 20, 23-26, 29, 36,
40, 54, 55, 60, 64, 66, 73)
-
Number of haploid daughter cells produced by meiosis
-
Number of ATP molecules required to add one nucleotide
during DNA replication
-
Number of kingdoms in the Eukarya domain
-
Number of major types of biological molecules
-
Number of phases in mitosis
-
Number of boxes in a monohybrid Punnett square cross
-
Number of nitrogenous bases in DNA
-
Number of letters in the genetic code
-
Number of pea plant traits Mendel selected to investigate
-
Number of chromosomes in pea plants

7 (30)

8 (43)
-
Total possible combinations of blood type genotypes

20 (53)
-
Total number of amino acids

23 (23, 24, 33)
-
Number of chromosomes in a haploid human cell

34 (30)
-
Total number of pea plant traits

35 (47)
-
If a mother is older than this age, the probability of
chromosomal abnormalities in her baby increase
dramatically

37 (36)
-
Number of green wrinkled pea plants in the F2 generation
when Mendel crossed pea shape and color
Science Power Guide | 84

46 (23, 24, 33)
-
Number of chromosomes in a diploid human cell

64 (59)
-
Maximum number of codons possible

113 (36)
-
Number of yellow wrinkled pea plants in the F2
generation when Mendel crossed pea shape and color

122 (36)
-
Number of green round pea plants in the F2 generation
when Mendel crossed pea shape and color

200 (41, 42, 78)
-
Normal blood cholesterol level for a young adult, in mg/dl
-
Lower limit of cholesterol levels in J.D.’s family
-
Number of genes on the Y chromosome

224 (35)
-
Number of white-flowered (recessive phenotype) pea
plants in the F2 generation when Mendel crossed whiteand purple-flowered pea plants

260 (12, 14, 25-27)
-
Number of cell types in an adult human

367 (36)
-
Number of yellow round pea plants in the F2 generation
when Mendel crossed pea shape and color

639 (35)
-
Number of pea plants Mendel used in his dihybrid cross of
pea shape and color

705 (35)
-
Number of purple-flowered (dominant phenotype) pea
plants in the F2 generation when Mendel crossed whiteand purple-flowered pea plants

782 (45)
-
Number of white-eyed male fruit fly offspring when
Morgan crossed a red-eyed F1 male and red-eyed F1
female

800 (41)
-
J.D.’s cholesterol exceeded this level, in mg/dl
-
Upper limit of cholesterol level in J.D.’s family

929 (35)
-
Number of F1 pea seedlings planted by Mendel when he
crossed white- and purple-flowered pea plants

1,011 (45)
-
Number of red-eyed male fruit fly offspring when Morgan
crossed a red-eyed F1 male and red-eyed F1 female

2,459 (45)
-
Number of red-eyed female fruit fly offspring when
Morgan crossed a red-eyed F1 male and red-eyed F1
female

3,000 (39, 78)
-
Average number of nucleotides in a single gene
-
Number of genes on chromosome 1

22,000193 (11, 26, 39, 59)
-
Number of genes in the human body

30,000 (31)
-
Total number of pea plants Mendel experimented with
193
Page 78 of the Resource Guide states that there are “about 22,500 genes” in the human body
Science Power Guide | 85

1 million (26)
-
Approximate number of eggs in the female ovary

3.1 million (76)
-
Number of base pairs unique to each human being

50 million (26)
-
Number of sperm cells produced daily by males

3.1 billion (11, 26, 27, 59, 78)
-
Number of nucleotides in the human body

50 trillion (9, 23, 25, 27)
-
Number of somatic cells in an adult human

64 trillion (26)
-
Total possible combinations of human chromosomes
FAHRENHEIT TEMPERATURES

72 to 80 (72)
-
Ideal temperature for Taq polymerase during polymerase
chain reaction (PCR)

50 to 60 (72)
-
Range of temperatures in which primers begin binding to
their complementary DNA sequences during the PCR process

95 (72)
-
Temperature at which DNA hydrogen bonds break
-
Developed by Aristotle
-
Suggested that the blending of the parents’ blood led to
the creation of an offspring in the female womb
-
Common explanation for inheritance of traits in the 18th
and 19th centuries
-
Suggested that offspring would have physical traits that
were a blend of the parent’s traits
-
Rejected by Mendel
-
Incorrect DNA replication model
-
Suggested that new DNA molecules consist of two new
strands
-
Incorrect DNA replication model
-
Suggested that DNA molecules consist of a mixture of old
and new strands
-
Proposed by James Watson and Francis Crick in 1953
-
Deoxyribose and phosphate form strands of DNA
-
Hydrogen bonds hold together complementary
nucleotide pairs
-
Proposed by Konstantin Mereschkowski in 1905
-
Mitochondria and chloroplasts evolved from symbiotic
prokaryotes that lived within eukaryotic cells
THEORIES AND MODELS






Aristotelian genetics (6)
Blending inheritance (6, 30,
36, 41)
Conservative replication (62)
Dispersive replication (62)
Double helix model (59, 60)
Endosymbiosis theory (18)
Science Power Guide | 86








Germ-plasm theory of
heredity (51)
-
Developed by August Weismann
-
Suggested that only germ plasm controls inheritance
-
Somatic and germ cells separate early in development and
are not interchangeable
-
First explanation of the genetics behind evolution
Hardy-Weinberg theorem
(52)
-
Developed by Wilhelm Weinberg and G.H. Hardy in 1908
-
Claims that a population’s allele frequencies will not
change if Hardy-Weinberg equilibrium is reached
Lamarckian inheritance (50,
51)
-
Developed by Jean-Baptiste Lamarck
-
Suggested that an offspring inherits traits that its parents
acquire during their lifetimes
Pangenesis (6, 50, 51)
-
Developed by Hippocrates and Darwin
-
Suggested that offspring formed from the parents’ organ
“seedlings”
-
Explained why offspring shared identical traits with their
parents
-
Developed by Thomas Cech and Sidney Altman
-
States RNA was the first genetic material on the early
Earth
-
Proposed by Watson and Crick
-
Widely accepted DNA replication model
-
States that DNA molecules consist of one old and one
new strand
-
The DNA molecule first unzips, then each old strand
serves as a template for a new strand
-
Erroneous theory developed by Phoebus Levene
-
Stated that DNA has an equal proportion of the four
nitrogenous bases
-
Led scientists to believe that DNA only aided the
structural stability of the genetic material
-
Disproved by Edwin Chargaff
-
Developed by Charles Darwin in his book On the Origin of
Species by Means of Natural Selection
-
Suggested that individuals with traits best suited to their
environment will survive and reproduce
-
Influenced by Darwin’s observations in the Galapagos
Islands
RNA world hypothesis (69)
Semi-conservative
replication (60-63, 80)
Tetranucleotide hypothesis
(55, 58)
Theory of evolution (6. 7. 9.
28, 30, 38, 48, 50, 51, 53, 54,
80, 82)
Science Power Guide | 87
PEOPLE—OTHER SCIENTISTS




Alfred Russel Wallace (7, 50)
Anton van Leeuwenhoek (9)
Carolus Linnaeus (9)
Charles Darwin (6, 7, 30, 50,
51, 80, 82)
-
British naturalist
-
Studied evolution of Australian and Asian species
-
Presented his ideas to the Linnean Society of London in
1858
-
First scientist to observe live cells
-
Analyzed pond water samples through a microscope
-
Founder of taxonomy
-
Classified all life into the animal, vegetable, or mineral
kingdoms
-
British naturalist
-
Developed the theory of evolution by natural selection
-
Travelled around the world on the H.M.S. Beagle from
1831 to 1836
-
Published On the Origin of Species by Means of Natural
Selection in 1859
-
Struggled to reconcile the differences between evolution
and commonly believed theories about inheritance

Harold Urey (10)
-
Demonstrated that simple molecules could form organic
molecules through simple chemical processes

J. Craig Venter (79)
-
Founder of Celera Genomics

Jean-Baptiste Lamarck (50)
-
French naturalist
-
Theorized that individuals inherit their parents’ acquired
traits

John Dalton (47)
-
First scientist to describe colorblindness194

Matthias Schleiden (9, 28)
-
German botanist
-
Co-founder of the cell theory
-
Scottish botanist
-
Discovered the cell nucleus using van Leeuwenhoek’s
drawings
-
Presented his findings to the Linnean Society of London in
1838
-
First scientist to observe cells
-
Could only see the cell wall of dried cork cells
-
Published his observations in Micrographia


194
Robert Brown (9)
Robert Hooke (9)
Dalton was color-blind as well. Colorblindness is sometimes referred to as Daltonism in his honor.
Science Power Guide | 88

Robert Koch (9)
-
First scientist to identify anthrax
-
Theorized that microorganisms cause infectious disease

Rudolf Virchow (9, 28)
-
Co-founder of the cell theory

Stanley Miller (10)
-
Demonstrated that simple molecules could form organic
molecules through simple chemical processes

Theodor Schwann (9, 28)
-
Co-founder of the cell theory

Udny Yule (52)
-
First scientist to theorize that a population’s allele
frequencies always add to one
-
Private company founded by J. Craig Venter
-
Attempted to complete the sequencing of the entire
human genome before the Human Genome Project could
ORGANIZATIONS

Celera Genomics (79)

Cold Spring Harbor
Laboratory (57)
-
Alfred Hershey and Martha Chase researched here

Columbia University (56)
-
Michael Dawson and Richard Sia researched here

Department of Energy (79)
-
One of two principal funders of the Human Genome
Project

Johns Hopkins University
(71, 72)
-
Hamilton Smith and Daniel Nathans researched here

Linnean Society of London
(9, 50)
-
Darwin, Wallace, and Brown presented their scientific
discoveries to this institution

National Center for Human
Genome Research (79)
-
Directed by James Watson and Francis Collins
-
Oversaw the Human Genome Project

National Institutes of Health
(79)
-
One of two principal funders of the Human Genome
Project

New York University (65)
-
Severo Ochoa researched here

Rockefeller University (56)
-
Oswald Avery researched here

Southwest Medical Center
(41)
-
Located in Dallas
-
14-year-old J.D. was a patient here

Stanford University (64)
-
Arthur Kornberg researched here

University of Vienna (30, 33,
37)
-
Mendel studied here
-
Erich von Tschermak’s grandfather taught botany here
Science Power Guide | 89
GENETIC TEST SUBJECTS







Bacteriophage (57, 58)
E. coli (58, 60, 61, 73)
Fruit flies (8, 45, 51, 78)
Grasshoppers (9, 45)
Pea plant (7, 8, 28, 30, 31,
35, 36, 37, 44-46, 48, 51, 76)
R-strain (56)
S-strain (56)
-
Virus that infects bacteria
-
Can reproduce by injecting its own genetic material into
the host’s chromosomes
-
Subject of Alfred Hershey’s and Martha Chase’s
experiments
-
Meselson and Stahl used this bacteria in their DNA
replication experiments
-
Used to mass produce insulin for diabetic patients
-
Latin name is Drosophila melanogaster
-
Eye color was studied by Thomas Morgan
-
Beloved by generations of AP Biology students
-
Studied by Estella Carothers
-
Testes served the first cytological evidence of Mendel’s
law of independent assortment
-
Scientists discovered sex chromosomes in 1910 by
studying their chromosomes
-
Subject of Gregor Mendel’s experiments
-
Latin name is Pisum sativum
-
Easy to cultivate
-
Reproduces quickly
-
Large flower size
-
Easy-to-manipulate pollination process
-
Mendel chose seven out of 34 possible physical traits to
experiment with
-
Subject of a dihybrid cross by William Bateson, Edith
Saunders, and Reginald Punnett
-
Has seven chromosomes
-
A non-virulent strain of Streptococcus pneumoniae
-
Lacks a polysaccharide capsule that protects the bacteria
from the immune system
-
A virulent strain of Streptococcus pneumonia
-
Contains a polysaccharide capsule that protects the
bacteria from the immune system

Streptococcus pneumoniae
(54, 55)
-
Bacteria responsible for most of the casualties during the
Spanish influenza pandemic

Tobacco plant (6)
-
Studied by Joseph Kolreuter in the 1760s
-
Subject of the first systematic genetic crosses
Science Power Guide | 90
ORGANIC MOLECULES










195
Adenine (54, 55, 58)
-
One of the four nitrogenous bases in DNA
-
Has a fused double-ring structure
Amino acids (10, 39, 54, 60,
64, 65, 68)
-
Building block of proteins
-
20 possible types
Antibody (42-44, 56, 67, 75)
-
Protein produced by the immune system
-
Binds and neutralizes a specific antigen
-
Group of three nucleotides in tRNA
-
Complements a mRNA codon
-
Triggers antibody production
-
In red blood cells, can be either A or B
-
Acronym for adenosine triphosphate
-
Cell’s primary energy source
-
Acts as a substrate for cyclic AMP
-
Adding a single nucleotide during DNA replication
requires four of these molecules
Carbohydrate (12, 13, 16, 20,
56, 57, 68)
-
One of the four major types of biological molecules
-
Provides energy to cells
Cholesterol (41, 42, 64)
-
A specific type of lipid
-
Insoluble in blood
-
Forms part of the plasma membrane
-
Used to synthesize sex steroids
-
Can be produced by all body cells in an energy-intensive
process
-
Mainly acquired through diet
-
Packaged with proteins within the liver to produce a LDL
cholesterol molecule
-
Acronym for cyclic adenosine monophosphate
-
Used as a second messenger in the neuron transmission
pathway195
-
One of the four nitrogenous bases in DNA
-
Has a fused double-ring structure
Anticodon (68)
Antigen (42, 43, 56)
ATP (14, 17, 26, 70, 75)
Cyclic AMP (56)
Cytosine (54, 55, 58)
For more details on the first and second signaling pathway, check out this link: http://tinyurl.com/n2l4kjf.
Science Power Guide | 91









196
-
Acronym for deoxyribonucleic acid
-
Stores the cell’s genetic information
-
Genetic material for all organisms except the RNA virus196
-
Can be inactivated by DNAse
-
Contains phosphorus but not sulfur
-
Has the appearance of a “viscous and slightly cloudy
solution”
-
Forms fibrous strands when mixed with ethanol
-
Hormone produced by the kidneys
-
Released when the blood has low oxygen levels
-
Stimulates the production of more blood cells
-
Can be mass produced using recombinant DNA
technology
-
Treatment for anemia
-
Protein with one or more sugar chains attached
-
Commonly found on the surface of red blood cells
Growth hormone (33, 36, 67,
75)
-
Treatment for short stature
-
Can be mass produced using recombinant DNA
technology
GTP (70)
-
Acronym for guanosine triphosphate
-
Cell’s energy source during protein synthesis
-
Part of the signal transduction pathway
-
One of the four nitrogenous bases in DNA
-
Has a fused single-ring structure
-
Protein that wraps around DNA
-
Can turn the gene on or off if modified
-
Hormone produced by the pancreas
-
Regulates blood sugar levels
-
Does not function correctly in diabetic patients
-
Protein produced by virus-infected cells
-
Increases other cells’ resistance to the attacking virus
-
Can be mass produced using recombinant DNA
technology
-
Treatment for those undergoing chemo- or radiation
therapy
DNA (10-13, 15-20, 24, 2628, 31, 32, 37, 43, 47-49, 54,
55, 57-80, 82)
Erythropoietin (75)
Glycoprotein (42)
Guanine (54, 55, 58)
Histone (77)
Insulin (67, 73-75)
Interferon (75)
As the name suggests, this virus has RNA instead of DNA as its genetic material. RNA viruses cause diseases such as SARS, hepatitis
C, West Nile fever, influenza, polio, and measles.
Science Power Guide | 92









LDL cholesterol (42. 64)
-
Acronym for low-density lipoprotein cholesterol
-
Consists of cholesterol molecules and protein
-
Produced by the liver for transport to cells
-
Clogs arteries when the LDL receptor mutates
-
One of the four major types of biological molecules
-
Nonpolar and hydrophobic
-
Separates organelles within the cell
-
Acronym for micro RNA
-
“Leftover” RNA molecules from non-coding regions of
DNA
-
Produced and discarded during transcription
-
Involved in cancer formation
-
Helps defend the cell against DNA and RNA viruses
-
Acronym for messenger RNA
-
Carries genetic information in the form of codons from
the nucleus to the ribosome
-
Adds a poly A tail and cap to both ends after transcription
-
RNA splicing removes intron regions of this molecule
before the molecule moves to the ribosomes
-
One of the four major types of biological molecules
-
Found in the nucleus
-
Contains genetic information
-
Discovered in 1869 by Friedrich Miescher
-
Has a high phosphorus content
-
Mixture of nucleic acids and chromosomal proteins
-
First observed by Friedrich Miescher in 1869
-
Has a high phosphorus content
Nucleotides (10, 11, 15, 20,
26, 32, 39, 58, 60, 62-64, 68,
70, 72, 73, 76, 79, 80)
-
Building block of DNA and RNA
-
Consists of phosphate, pentose sugar, and a single
nitrogenous base
Phospholipid (10, 12-14, 17)
-
Lipid molecule
-
Forms the plasma membrane of cells
-
Each molecule has a hydrophilic phosphate “head” and
two hydrophobic fatty acid “tails”
-
Nucleotide made of adenine
Lipid (12, 16, 20, 39, 42, 57,
68)
miRNA (70)
mRNA (60, 64-68, 70, 79, 80)
Nucleic acid (10, 12, 54, 56,
57, 60, 80)
Nuclein (54, 65)
Poly A tail (68)
Science Power Guide | 93








Primer (62, 63, 73)
Protein (12-14, 16, 17, 21,
22, 27-29, 31, 33, 36, 39, 40,
42, 43, 54, 57, 58, 60-71, 73,
75, 78, 80)
rRNA (13, 16, 20, 65, 66)
Ribozyme (69)
RNA (10, 12, 13, 16, 20, 32,
54, 57, 62, 63, 65-67, 69, 80,
73, 80)
siRNA (70)
Steroid (16, 42, 65)
Thymine (54, 55, 58, 65, 80)
-
Nucleic acid strand
-
Complements a specific DNA sequence
-
Used in DNA replication
-
Replaced by DNA fragments at the end of DNA replication
-
One of the four major types of biological molecules
-
Used in transportation, substance recognition, signal
transmission, and enzymatic reactions
-
Initially believed to be the genetic material passed from
parent to offspring
-
Produced by a combination of any of 20 amino acids
-
Contains sulfur but not phosphorus
-
Acronym for ribosomal RNA
-
Produced in the nucleolus
-
Clumps with proteins to form ribosomes
-
Holds mRNA and tRNA in the correct position for protein
synthesis
-
Involved in post-transcription RNA processing and protein
synthesis
-
Can splice itself
-
Family of nucleic acids
-
Involved in protein synthesis
-
Single stranded
-
Made of ribose sugar
-
Smaller in size than DNA
-
Believed to be the first genetic material
-
Produced in the nucleus
-
Can form double-stranded structures if necessary
-
Hydrogen bonds link the nucleotide pairs
-
Involved in enzymatic and catalytic activities
-
Acronym for short interfering RNA
-
Can be abbreviated as RNAi
-
Produced when enzymes digest double-stranded RNA
-
Involved in gene expression, cancer formation, and
defense against DNA and RNA viruses
-
Lipid molecule
-
Has a ring structure
-
Primarily functions as a hormone
-
One of the four nitrogenous bases in DNA
-
Has a fused single-ring structure
Science Power Guide | 94


tRNA (60, 61, 65, 66, 68, 69,
80)
Uracil (54, 65, 80)
-
Acronym for transfer RNA
-
Carries the complementary anticodon to a mRNA codon
-
Involved in protein synthesis
-
Often forms double-stranded structures
-
One of the four nitrogenous bases in RNA (replaces
thymine)
-
Has a fused single-ring structure
-
Adds phosphate into gaps in the phosphate-sugar
backbone
-
Zips up the new DNA strand with the parent DNA strand
-
Adds complementary nucleotides to the new DNA strands
-
Taq polymerase is one type of this enzyme
ENZYMES


DNA ligase (61)
DNA polymerase (62, 63, 73)

DNAse (57)
-
Digests DNA

Endonuclease R (71)
-
Type of restriction enzyme
-
Can cut DNA at specific sites
-
Unzips the DNA double helix
-
Creates a replication fork and bubble at the starting point
of replication
-
Type of restriction enzyme
-
Cuts between two adenine bases only in the pattern
AAGCTT


Helicase (62, 67, 73)
Hind III (70, 72)

Nuclease (62, 71)
-
Removes incorrect nucleotides during DNA replication

Primase (62, 63, 73)
-
Synthesizes and attaches RNA primers to replicating DNA
strands

Restriction enzyme (70-72,
75, 76, 80)
-
Found in all species
-
Cuts DNA between specific nucleotides
-
Studied by Werner Arber, Hamilton Smith, and Daniel
Nathans
-
Involved in restriction fragment length polymorphism
-
Type of DNA polymerase
-
Can withstand high temperatures
-
Used in the polymerase chain reaction

Taq polymerase (74)
Science Power Guide | 95
RADIOACTIVE TRACERS








N (61, 62)
N (61, 62)
P (58)
S (58)
-
Acronym for nitrogen-14
-
Used as a radioactive tracer in Meselson and Stahl’s E. coli
experiments
-
Also known as the “light isotope”197
-
Acronym for nitrogen-15
-
Used as a radioactive tracer in Meselson and Stahl’s E. coli
experiments
-
Also known as the “heavy isotope”
-
Acronym for phosphorus-32
-
Injected into bacteriophages as part of the Hershey and
Chase experiment
-
Only incorporated into DNA
-
Could be extracted from the host bacteria
-
Acronym for sulfur-35
-
Injected into bacteriophages as part of the Hershey and
Chase experiment;
-
Only incorporated into protein
-
Remained in the bacteriophage during the experiment
GREEK AND LATIN WORDS

Anaphase (20, 22, 24, 25, 29,
37)
-
Greek; ana—“up”

Autophagy (16)
-
Greek, auto—“self”; phagein—“to eat”

Chromosome (7, 8, 12, 16,
18, 19-29, 31-33, 36, 37, 39,
45-47, 49-51, 54, 57, 60, 61,
76, 78-80)
-
Greek; chromo—“color”; some—“body”

Cytokinesis (19, 20, 22, 24,
25, 27, 29)
-
Greek; cyto—“cell”; kine—“move”

Epigenetics (5, 77, 81)
-
Greek, epi—“above, on top of”

Eukaryote (11-16, 19, 20, 22,
24, 29, 32, 58, 60, 62, 66-68)
-
Greek; eu—“true”; karyo—“nucleus”

Filius (33)
-
Latin; “son”

In utero (48)
-
Latin; “in the womb”
197
There are two stable isotopes of nitrogen, and nitrogen-14 happens to be just a bit lighter than nitrogen-15.
Science Power Guide | 96

Lysosome (16, 20)
-
Greek; lyse—“split”

Metaphase (20-22, 24-26,
29)
-
Greek; meta—“in the middle of”

Mitosis (7, 18, 19-24, 27-29,
50, 80)
-
Greek; “thread”

Pangenesis (6, 50, 51)
-
Greek for “whole birth”

Pleiotropy (44, 49)
-
Greek; pleio—“many”; tropic—“affecting”

Prokaryote (10-14, 16, 18,
19, 28, 29, 32, 47, 58, 60- 62,
67)
-
Greek; pro—“before”; karyo—“nucleus”

Prophase (20-22, 24-26, 29)
-
Greek; pro—“earlier, before”

Telophase (20, 22, 24, 25,
29)
-
Greek, telo—“end”

Thermophilic (73)
-
Greek; thermo—“heat”; philia—“like”
PERCENTAGES

1% (44)
-
Fewer than one percent of Americans carry the BRCA1 or
BRCA2 genes

5% (11, 78)
-
Percentage of human genes that actively code for
proteins198
-
Percentage of the Human Genome Project budget set
aside for potential ethical, legal, and social issues
-
Less than ten percent of breast cancer cases occur due to
BRCA1 and BRCA2 mutations
-
Percentage of dividing cells that undergo mitosis at any
point in time

10% (44)

20% (57)
-
Percentage of adenine and thymine in human DNA

22% (57)
-
Percentage of adenine and thymine in dog DNA

28% (57)
-
Percentage of cytosine and guanine in dog DNA

30% (57)
-
Percentage of cytosine and guanine in human DNA

90% (20, 24, 79)
-
Percentage of time the cell spends in interphase
-
Percentage of time prophase I takes up of both meiosis I
and II
-
Percentage of the HGP published in a 2000 rough draft
198
USAD mentions that “slightly more than 2% of our entire genome” codes for proteins on page 39.
Science Power Guide | 97

99.9% (75)
-
Percentage of nucleotides all humans share
-
Percentage of eukaryotes that have adopted sexual
reproduction
-
Constantly undergoes interphase and mitosis
-
Occurs in areas with frequent cell death, such as the skin,
intestines, and uterus
-
Only 10% of these cells reproduce at any given time to
ensure smooth and continuous functioning of the human
body
-
Either a sperm or egg cell
-
Passes genetic material from parent to offspring
-
Originates from germ cells
-
Haploid
-
Sometimes known as a gonadal gamete
-
Reproductive cell of multicellular organisms
-
Migrates to the sexual organs in the early embryonic stage
-
Remains dormant until sexual maturity
TYPES OF CELLS



Dividing cell (19, 26, 27)
Gamete (22-25, 29, 35-37,
40, 46, 51, 54, 82)
Germ cell (23, 25, 26, 36, 51,
77, 79)

Multipotent cell (26)
-
Can form a limited range of specialized cell types within a
tissue

Non-dividing cell (27)
-
Permanently exits the cell cycle under normal conditions
-
Resides in the G0 phase
-
Operates continuously without any interruptions
-
Also known as a terminally differentiated cell
-
Includes nerve cells in the brain, heart muscle cells. and
eye lens cells
-
Immature female gamete
-
Diploid
-
Undergoes gametogenesis
-
Can form into any of the 260 types of cells
-
Cannot produce an entire functional organism
-
Divided into one of three germ layers
-
Studied by Karl Landsteiner
-
Delivers oxygen to cells
-
Glycoprotein attaches to its surface
-
Both A and B antigens are expressed on its surface



Oogonia (23, 25)
Pluripotent cell (27)
Red blood cell (39, 42-44,
64)
Science Power Guide | 98





Reproductively dormant cell
(27)
Somatic cell (16, 18, 23, 26,
27, 31, 33, 50, 51, 76)
Spermatogonia (23, 25)
Stem cell (11, 26, 29, 77)
Totipotent cell (26)
-
Normally remains reproductively inactive
-
Can re-enter the cell cycle under certain conditions
-
Liver cells are reproductively dormant
-
Body cell
-
Contains 46 chromosomes
-
Diploid
-
Can become a pluripotent stem cell
-
Immature male gamete
-
Diploid
-
Undergoes gametogenesis
-
Can form any of the 260 types of cells
-
Replaces dead or non-functioning cells
-
Can divide infinitely
-
Can be used to treat Alzheimer’s and heart diseases
-
Daughter stem cell can remain as a reserve stem cell or
become a specialized cell
-
Can form any of the 260 types of cells
-
Can produce an entire functional organism

White blood (53)
-
Studied by Friedrich Miescher

Zygote (11, 23, 25, 26)
-
Formed by the fusion of a sperm and egg cell
-
Divides by mitosis to produce all of an adult human’s
somatic cells
-
One of several forms of a gene
-
Usually found in pairs
-
Can be either dominant or recessive
-
Used by Mendel to describe the heritable “factor” that
controlled inherited traits
-
Different forms arise due to mutation and evolutionary
adaptation
-
Non-sex eukaryotic chromosome
-
Describes chromosomes 1-22
-
Inherits a genetic trait or mutation but does not express it
-
Has a heterozygous dominant genotype for the trait or
mutation
GENETICS TERMS



Allele (25, 31-33, 35-37, 39,
40-46, 52-54, 64, 80)
Autosome (32, 33, 45)
Carrier (39, 47, 48, 70, 77)
Science Power Guide | 99

Chromatid (18, 20-22, 24-26,
46)
-
One copy of a duplicated chromosome produced during
DNA replication

Codon (60, 64, 65)
-
Group of three nucleotides in mRNA molecules
-
Codes for a specific amino acid
-
Comes in 64 possible types
Dihybrid cross (32, 33, 35,
37, 40, 45)
-
Cross in which parents differ in two traits
-
Mendel conducted this type of cross with round/wrinkled
and yellow/green peas
Diploid (20, 23-25, 27, 3133, 36)
-
Cell with a full set of chromosomes (46 in humans)
-
All somatic cells are diploid
Dominant (30-36, 39-43, 45,
49, 52)
-
One of two forms of an allele
-
Determines the phenotype when the organism has a
heterozygous genotype
-
Written as a capital letter
-
Regions of DNA that code for proteins
-
Form part of the mRNA molecule
-
Sent to the ribosomes for protein synthesis
-
Follows the P generation
-
Short for “first filial generation”
-
Always contains one, never both, traits from the P
generation
-
Follows the F1 generation
-
Product of self-fertilization in the F1 generation
-
Displays a phenotype ratio of 3:1 if a monohybrid cross is
conducted
-
Displays a phenotype ratio of 9:3:3:1 if a dihybrid cross is
conducted
-
Occurs when one nucleotide is added or deleted
-
All subsequent codons are affected
-
Could lead to significant changes in the amino acid
sequence
-
Set of nucleotides
-
Codes for one or more proteins
-
Process in which genetic information in DNA is converted
to a mRNA molecule, then a protein
-
Can be regulated by siRNA









Exons (60, 68)
F1 generation (32-36, 40, 45,
51)
F2 generation (32-35)
Frameshift mutation (64)
Gene (everywhere)
Gene expression (67, 70, 81)
Science Power Guide | 100

Genetic code (58, 60, 65, 68,
69, 80)
-
Relates codons in mRNA to specific amino acids
-
Consists of four letters (A, T, G, C)
-
Studied by Thomas Cech and Sidney Altman

Genetic map unit (46)
-
Distance between any two genes on a chromosome

Genotype (31, 32, 39, 40, 4244, 47, 51-53, 80)
-
Pair of alleles that determine a particular trait
-
In a non-evolving population, dominant homozygous,
dominant heterozygous, and recessive homozygous
genotypes appear in a 1:2:1 ratio

Haploid (23-25, 27, 29, 32,
36, 37, 60, 76)
-
Cell with half a full set of chromosomes (23 in humans)

Hardy-Weinberg equation
(52, 53, 80)
-
  2     1, with p and q representing the
dominant and recessive alleles for a gene, respectively

Hardy-Weinberg equilibrium
(52, 53)
-
Defines the conditions for a non-evolving population
-
The population must be large to ensure minimal changes
in allele frequency
-
No immigration or emigration can occur
-
Population members mate randomly
-
No new mutations occur
-
No natural selection occurs
-
If any of the Hardy-Weinberg equilibrium conditions are
not met, the population undergoes microevolution

Heterozygous (31-33, 35, 39,
52)
-
Describes an individual with two different alleles at a
specific locus on a pair of homologous chromosomes

Homologous chromosomes
(24, 25, 31-33, 35-37)
-
Pair of chromosomes with the same set of genes
-
One chromosome in each pair comes from each parent

Homozygous (24, 25,31-33,
35-37)
-
Describes an individual with two identical alleles present
on both homologous chromosomes

Human Genome Project (38,
76, 78, 81, 82)
-
Sequenced the entire human genome
-
Funded by the National Institutes of Health and the
Department of Energy
-
Initiated in October 1990
-
Completed in 2003 ahead of schedule and below budget
-
Directed by James Watson and Francis Collins
-
Affected almost all areas of society
-
Offspring of two parents of different species

Hybrid (7, 30-33, 35, 37, 40,
45, 61, 62)
Science Power Guide | 101

Introns (60, 63, 68)
-
Non-coding regions of DNA

Locus (31, 32, 36)
-
Gene’s location in the DNA molecule

Missense mutation (63)
-
Occurs when a single nucleotide substitution changes the
coded amino acid

Monohybrid cross (32-35,
40)
-
Cross with parents differing in one trait
-
Mendel conducted this type of cross with purple- and
white-flowered plants
Mutation (8, 26, 28, 29, 32,
36-39, 42, 44, 45, 47, 48, 51,
52, 54, 63-65, 76, 77, 79, 80,
82)
-
Error in DNA replication
-
Can be inconsequential, beneficial, or harmful
-
Occurs randomly
-
Probability of occurrence increased by many
environmental and metabolic factors
-
Main source of genetic variation


Nonsense mutation (64)
-
Occurs when a single nucleotide substitution turns an
amino-acid-coding codon into a stop codon

P generation (32, 33)
-
First generation in an experiment
-
Consists of purebred organisms
-
Short for parental generation
-
Physical trait of an organism
-
Controlled by one or more genotypes
-
In a non-evolving population, dominant and recessive
phenotypes will appear in a 3:1 ratio

Phenotype (31-33, 35-38,
40-45, 51, 52, 54, 76)

Polyploidy (54)
-
Occurs when organisms have more than two homologous
chromosomes

Population genetics (9, 35,
38, 51, 53, 80)
-
Study of a population’s genes and genotypes

Punnett square (40, 45-48)
-
Diagram that predicts the probability of an offspring
inheriting a specific genotype
-
Developed by Reginald Punnett
-
One of two forms of an allele
-
Only expressed under homozygous conditions
-
Indicates the presence of a mutated gene
-
Written as a lowercase letter
Segregation (8, 32, 35-37,
48, 54)
-
Separation of alleles during meiosis
-
Described by Mendel’s law of segregation
Self-fertilization (32, 33, 35)
-
Fertilization between the sperm and egg of the same
flower



Recessive (8,31-36, 38-43,
47, 49, 52, 64)
Science Power Guide | 102

Sex chromosome (8, 32, 33,
45, 46)
-
Determines the offspring’s sex
-
Describes chromosome 23
-
Contains linked genes
-
Discovered in grasshopper chromosomes in 1910

Silent mutation (64)
-
Does not change the amino acid sequence being
translated

SNP (76, 77, 79)
-
Acronym for single nucleotide polymorphism
-
Refers to a single point mutation
-
Differentiates genomes among different human beings
-
Can be cut by restriction enzymes
-
Group of three nucleotides
-
Signals the cell to stop translation
-
Includes UAA, UAG, and UGA
-
Group of three nucleotides
-
Signals the cell to begin translation
-
Also codes for methionine
-
Includes AUG


Start codon (60, 68)
Stop codon (60, 64, 68)

Synapse (24)
-
Point at which two homologous chromosomes attach
during prophase I

Test cross (33, 36, 45)
-
Cross of a homozygous or heterozygous dominant
individual with a homozygous recessive individual

Tetrad (24)
-
Group of two pairs of homologous chromosomes
-
Forms during prophase I of meiosis
-
Randomly orients during metaphase I
-
"Tetra" means "four" in Greek
-
Cross involving two parents with identical genotypes
-
Produces offspring with identical genotypes as the
parents
-
Describes the P generation of Mendel’s experiments
-
One of the two human sex chromosomes
-
Two X chromosomes create a female offspring


True-breeding (30, 32)
X chromosome (8, 45, 46,
47)
Science Power Guide | 103

Y chromosome199 (46, 47,
49)
-
One of the two human sex chromosomes
-
One X and one Y chromosome create a male offspring
-
Contains fewer than 200 genes
-
Controls sex determination and male fertility
-
Carries the SRY gene
-
Used to trace male lineage
PATTERNS OF INHERITANCE

Co-dominance (42-43, 49)
-
Occurs when multiple alleles can be expressed
simultaneously

Incomplete dominance (4042, 48)
-
Occurs when no single allele is dominant or recessive
-
Leads to a blending of the two alleles
-
Crossing red and white flowers leads to pink offspring
-
Genes that are located close together on the same
chromosome
-
Discovered by William Bateson, Edith Saunders, and
Reginald Punnett
-
Existence confirmed by Thomas Morgan and Alfred
Sturtevant
-
Do not follow Mendel’s law of independent assortment

Linked genes (8, 37, 44-46,
49)

Pleiotropy (44, 49)
-
Occurs when a single gene controls multiple traits

Polygenic inheritance (44,
49)
-
Occurs when multiple genes control a single trait
-
Usually found in quantitative traits with a range of
continuous values
-
One of the rules of probability used by Mendel
-
Also known as the sum rule
-
If two events are mutually exclusive200, then the probability
of either occurring is the sum of the probabilities of each
occurring individually
LAWS AND PRINCIPLES

199
Addition rule (33, 35)
USAD states that the Y chromosome is the smallest (pg. 78 of the Resource Guide), but the National Institutes of Health website
points to chromosome 21 as the smallest.
200
Two events are mutually exclusive if they cannot occur at the same time. For example, flipping a coin will result in either heads or
tails, but not both. Mathematically speaking, if A and B represent two events, then P (A and B) = 0
Science Power Guide | 104
-
Algebraic theorem
-
Describes the expansion of algebraic expressions with the
form   
-
Mendel used this equation with n=2, in the form
      2  
-
Developed by Edwin Chargaff
-
States that adenine and guanine always pair with thymine
and cytosine, respectively
-
States that, if two purebred parents are crossed, only one
form of the parent’s traits will appear in the offspring
-
Developed by Mendel
-
States that alleles of different traits are distributed to sex
cells independently of one another
-
Developed by Mendel
-
States that pairs of alleles separate and recombine during
fertilization
-
Developed by Mendel
-
One of the rules of probability used by Mendel
-
Also known as the product rule
-
If two events are independent201, then the probability of
both occurring is the product of the probabilities of each
occurring individually
Experiments on Plant
Hybridization (36)
-
Published by Mendel in 1866
-
Described the results of his pea plant experiments

Genetics and the Origin of
Species (54)
-
Published by Theodosius Dobzhansky

On the Origin of Species by
Means of Natural Selection
(50)
-
Published by Charles Darwin in 1859
-
Describes Darwin’s theory of evolution by natural selection
The Evolutionary Synthesis
(54)
-
Published by Ernst Mayr
-
Described the importance of synthesizing Mendelian
genetics and evolution
-
Explained the connection between genetic variation and
evolutionary change






Binomial theorem (33-35)
Chargaff’s rule (58)
Law of dominance (35, 36,
48)
Law of independent
assortment (8, 36, 37, 45, 48)
Law of segregation (8, 3537, 48)
Multiplication rule (33, 36)
SCIENTIFIC WORKS


201
Two events are independent if the occurrence of one does not affect the probability of another. For example, rolling a 6 on the first
roll of a die does not affect the likelihood that you will roll a 6 the next time.
Science Power Guide | 105
CELLULAR PROCESSES


Agglutination (42)
Asexual reproduction (19,
20, 22, 24, 29)
-
Clumping of red blood cells
-
Occurs when antibodies attack antigens of the same
blood type
-
Leads to red blood cell destruction
-
Involves only one parent
-
Does not require gamete fusion
-
Usually produces genetically identical offspring

Autophagy (16)
-
Process in which lysosomes destroy and recycle the cell’s
worn structures

Binary fission (19, 20, 29)
-
Prokaryotic reproduction process
-
Parent clones itself to create a genetically identical
daughter cell
-
Form of asexual reproduction

Budding (20)
-
One form of eukaryotic asexual reproduction

Cell cycle (19, 20, 27-29, 73,
78, 82)
-
Series of events in all eukaryotic cells
-
Produces two daughter cells from one parent cell
-
Divided into interphase and mitosis
-
Requires 20 to 24 hours to complete

Cellular respiration (17)
-
Process in which cells break down food molecules and
transform them into energy

Cleavage (22)
-
Final splitting of the cell membrane during cytokinesis
-
Contraction of microfilaments and microtubules
-
Forms a cleavage furrow

Conjugation (71)
-
Transfer of DNA from one bacterium to another

DNA methylation (77)
-
Addition of a methyl group to the DNA phosphate-sugar
backbone
-
May turn the gene on or off
-
Prevents transcription from occurring properly if added to
a nucleotide
-
Process in which solid and liquid particles enter the cell
-
Cell completely engulfs the particle
Fertilization (23, 25, 26, 29,
30, 32, 35, 36, 48)
-
Fusion of a haploid sperm and egg cell
-
Produces a diploid zygote with half its genome from each
parent
Fission (19, 20, 29)
-
One form of eukaryotic asexual reproduction



Endocytosis (16, 42)
Science Power Guide | 106










Gametogenesis (23, 29)
Histone modification (78)
Meiosis (23-27, 29, 32, 36,
37, 40, 45, 50, 80
Mitosis (7, 18-24, 27-29, 50,
80)
Phagocytosis (17)
Photosynthesis (11, 17)
Pinocytosis (17)
Regeneration (20)
Sexual reproduction (19, 20,
22, 24, 29, 50, 60)
Transcription (16, 65, 66-70,
78, 80)
-
Process in which spermatogonia and oogonia mature to
become gametes
-
One step in this process is meiosis
-
Caused by external environmental or chemical factors
-
Can turn the gene on or off by binding the histones
tighter or looser around DNA
-
Reproductive process of germ cells in multicellular
organisms
-
Based on Mendel’s law of segregation
-
One parent cell produces four daughter cells
-
Eukaryotic asexual reproduction
-
More complex than binary fission due to presence of a
nuclear envelope and subcellular organelles
-
Four major phases are prophase, metaphase, anaphase,
and telophase
-
Process in which cells ingest solid particles
-
Specific form of endocytosis
-
Process in which visible light synthesizes energy molecules
such as ATP and glucose
-
Occurs only in plants and certain bacteria
-
Process in which cells ingest liquid particles
-
Specific form of endocytosis
-
One form of eukaryotic asexual reproduction
-
Cell division produces a new body or body parts
-
Form of reproduction involving the fusion of two haploid
gametes
-
Produces genetically diverse offspring
-
Encourages the spread of beneficial traits that ensure a
species’ survival
-
Transmission of genetic information from the DNA to a
mRNA molecule
-
Involves the three steps of initiation, elongation, and
termination
Science Power Guide | 107

Translation (16, 60, 65, 68,
70, 71, 79, 80)
-
Another name for protein synthesis
-
Final step in gene expression
-
tRNA “translates” the DNA/RNA language into the
language of proteins
-
Includes the three steps of initiation, elongation, and
termination
-
Once complete, proteins are delivered to their final
destination or modified further in the endomembrane
system
-
One of the four major steps of mitosis
-
Sister chromatids separate into individual chromosomes
-
Kinetochore microtubules pull chromosomes towards
opposite poles until the poles have an equal number of
chromosomes
-
Polar microtubules elongate the cell
-
One of the four steps in meiosis I
-
Homologous chromosomes separate
-
Spindle microtubules pull the chromosomes towards the
poles
-
Sister chromatids remain attached at the centromere and
move as a whole unit
-
Final step of mitosis
-
In animal cells, the plasma membrane breaks into two
through cleavage
-
In plant cells, membrane-bound vesicles containing
cellulose align and fuse to form a new cell wall
-
One of two steps in prophase
-
Involves the condensation of sister chromatids and
nucleoli disassembly
-
Spindle microtubules push centrosomes toward opposite
poles
-
Resting state
-
Exists outside of the cell cycle
-
Cells in this phase remain reproductively inactive
-
Non-dividing and reproductively dormant cells are usually
found in this phase
PHASES OF THE CELL CYCLE





Anaphase (20, 22, 24, 25, 29,
37)
Anaphase I (24, 37)
Cytokinesis (19, 20, 22, 24,
25, 27, 29)
Early prophase (20)
G0 phase (27)
Science Power Guide | 108








G1 phase (20, 27, 29)
G2 phase (20, 24, 27, 29)
Interphase (20, 24, 27-29)
Late prophase (20, 21)
Meiosis II (24)
Metaphase (20-22, 24-26,
29)
Metaphase I (24, 26)
Prophase (20-22, 24-26, 29)
-
One of three phases in interphase
-
All cytoplasmic organelles replicate
-
RNA and protein synthesis occurs frequently
-
One of three phases in interphase
-
Replicated subcellular organelles assemble
-
Consists of 90% of the cell cycle
-
Includes the G1, S, and G2 phases
-
Involves the synthesis and assembly of all non-genetic
organelles, molecules, and structures
-
One of the four major steps of mitosis
-
Also known as prometaphase
-
Nuclear envelope disassembles into vesicles
-
Chromatids produce a kinetochore complex near the
centromeres
-
Kinetochore microtubules separate the sister chromatids
-
Polar microtubules elongate the cell and push the
centrosomes to the poles
-
Involves four major stages (prophase II, metaphase II,
anaphase II, and telophase II)
-
Almost identical to mitosis, but involves non-identical
sister chromatids
-
Produces four haploid cells
-
One of the four major steps of mitosis
-
Chromosomes align along the center of the cell
-
Kinetochore microtubules drag the chromatids to the
metaphase plate
-
Polar microtubules elongate the cell
-
One of the four steps in meiosis I
-
Tetrads randomly orient at the metaphase plate
-
Random and independent chromosome shuffling fosters
increased genetic diversity
-
One of the four major steps of mitosis
-
Divided into early and late prophase
Science Power Guide | 109




Prophase I (24)
S phase (20, 24, 60, 73)
Telophase (20, 22, 24, 29)
Telophase I (24)
-
One of the four steps in meiosis I
-
Mitosis and meiosis are identical except for the events of
this phase
-
Pairs of homologous chromosomes form tetrads
-
Non-sister chromatids cross over to form synapses
-
Maternal and paternal alleles exchange genetic
information at random locations on the chromatids
-
Longest phase of meiosis
-
Takes 90% of the total time for meiosis I and II
-
One of three phases in interphase
-
Acronym for synthesis phase
-
The parent cell genome replicates
-
Individual chromosomes divide into two sister chromatids
linked by a centromere
-
One of the four major steps of mitosis
-
Almost the complete opposite of prophase
-
New chromosomes begin to disperse
-
Nuclear envelope reforms
-
Spindle microtubules and centrosomes disintegrate
-
One of the four steps in meiosis I
-
All 23 chromosomes migrate to the location of the
daughter cell’s future nucleus
-
Cytokinesis occurs briefly before meiosis II begins
ENVIRONMENTAL PROCESSES

Allopatric speciation (53)
-
Formation of a new species through geographic isolation

Gene shuffling (22)
-
Exchange of genetic material between different cells or
organisms
-
First occurred 2 billion years ago

Genetic drift (54)
-
Random change in a population’s allele frequency

Microevolution (53, 54, 64,
80)
-
Occurs when a population’s allele frequency changes

Speciation (53, 64)
-
Process leading to the creation of a new species
-
Also known as macroevolution
-
Formation of a new species when both the old and new
species share the same geographic region
-
Occurs in plants
-
Can be caused by polyploidy or meiotic errors

Sympatric speciation (54)
Science Power Guide | 110
DISEASES AND DISORDERS






202
Albinism (44)
-
Occurs when a gene that codes for a melanin-producing
enzyme mutates
-
Example of pleiotropy
-
Also known as black urine disease
-
Discovered by Dr. Archibald Garrod in 1902
-
First disease linked to genes
-
Occurs when a gene that codes for an amino acid
metabolism enzyme mutates
-
Leads to excessive metabolite202 in the blood and urine
-
Damages cartilage, heart valves, and kidneys
-
Garrod called this disease an “inborn error of metabolism”
-
Urine of patients with this disease turns dark brown upon
exposure to oxygen
-
Individuals that carry BRCA1 or BRCA2 are at increased
risk for this disease
-
Individuals with two or more close relatives that suffered
from this disease are also at risk
Cancer (5, 27-29, 44, 49, 64,
70, 78)
-
Disease caused by abnormally rapid cell growth
-
Results when oncogenes or other cell-cycle related genes
mutate
Colorblindness (47, 49)
-
Example of polygenic inheritance
-
First described by John Dalton in 1794
-
Most common form is red-green
-
Caused by a recessive allele on the X-chromosome
-
Affects more males than females (10:1 ratio)
-
Most common deadly genetic disease affecting
Caucasians in the United States
-
Affects one in 2,500 people with Northern or Central
European ancestry
-
Occurs when a gene that codes for a protein channel on
the cell surface mutates
-
Leads to mucus accumulation in the lungs and digestive
system
-
Can cause infections and digestion problems
-
Dr. Francis Collins directed the project that sequenced the
gene controlling this disease in 1999
Alkaptonuria (38)
Breast cancer (44)
Cystic fibrosis (39, 48, 79)
More specifically, homogentisic acid and alkapton
Science Power Guide | 111

FH (41)
-
Acronym for "familial hypercholesterolemia"
-
Occurs when the bloodstream contains unusually high
cholesterol levels
-
Inherited as an autosomal dominant trait
-
Leads to heart attacks in people as young as 20
-
Causes heart disease and hypertension later in life
-
Afflicts 1 in 500 Americans, including 14-year old J.D.

Ovarian cancer (44)
-
Individuals that carry BRCA1 or BRCA2 are at increased
risk for this disease

Sickle-cell anemia (39, 48,
49, 64)
-
Most common genetic disease in the United States
-
Affects one in 400 African Americans
-
Occurs when a single nucleotide substitution adds the
wrong amino acid to hemoglobin
-
Red blood cells become sickle-shaped and cannot fit
through the capillaries
-
Can lead to multiple organ failure
-
Affects one in 3,500 Ashkenazi Jews
-
Occurs when a single gene mutation alters a lipid
metabolism enzyme
-
Neural impulses cannot be transmitted correctly
-
Leads to paralysis, blindness, deafness, and other
neurological disorders
-
Occurs when an individual’s pancreas cannot produce
insulin
-
Treated with insulin injections
-
Occurs when an individual’s body cells do not respond to
insulin
-
Treated with insulin injections
-
Example of a co-dominant trait
-
Both alleles are expressed simultaneously
-
The gene that controls this trait codes for glycoproteins
on the red blood cell surface



Tay-Sachs disease (39)
Type I diabetes (75)
Type II diabetes (75)
PHYSICAL TRAITS

Blood type (42, 43)

Earlobe attachment (38)
-
Example of a human trait controlled by one gene

Flower color (33, 34, 45, 51,
52)
-
One of seven traits Mendel investigated in pea plants
-
One of two traits investigated by Edith Saunders, Reginald
Punnett, and William Bateson
Science Power Guide | 112

Flower position (30)
-
One of seven traits Mendel investigated in pea plants

Fruit fly eye color (45, 46)
-
Thomas Morgan studied this trait in fruit flies
-
Can be either red or white
-
Alleles for this trait are linked to the offspring’s sex
-
An X-chromosome mutation triggers white eye color

Hitchhiker’s thumb (38)
-
Example of a human trait controlled by one gene

Human eye color (47)
-
Example of polygenic inheritance

Human height (44)
-
Example of polygenic inheritance
-
Can be influenced by nutrition, hormone levels, and other
environmental factors

Human skin color (44)
-
Example of polygenic inheritance

Pea shape (30)
-
One of seven traits Mendel investigated in pea plants

Pea color (30)
-
One of seven traits Mendel investigated in pea plants

Pea pod color (30)
-
One of seven traits Mendel investigated in pea plants

Pea pod shape (30)
-
One of seven traits Mendel investigated in pea plants

Pea pollen grain shape (44)
-
One of two traits investigated by Edith Saunders, Reginald
Punnett, and William Bateson

Plant height (30, 33)
-
One of seven traits Mendel investigated in pea plants

Rh factor (43, 44)
-
Antigen found on the red blood cell surface
-
Used as a form of blood typing
-
First identified in the Rhesus monkey
-
Can be either positive (+) or negative (-)
-
Rh positive dominates over Rh negative
-
Determined by the presence of the Y chromosome and
the SRY gene in humans
-
Determined by the number of X chromosomes in fruit flies
-
Example of a human trait controlled by one gene
-
Occurs when individuals have two A alleles or one A and
one O allele
-
Has A antigens on red blood cells
-
Blood produces anti-B antibodies
-
Can accept type A and AB blood
-
Can donate blood to type A and O individuals


Sex (46)
Widow’s peak (38, 43)
BLOOD TYPES

A (42, 43)
Science Power Guide | 113



AB (43)
B (42, 43)
O (43)
-
Occurs when individuals have one A and one B allele
-
Has both A and B antigens on red blood cells
-
Blood produces no antibodies
-
Can accept any type of blood
-
Can donate blood to type AB individuals
-
Example of co-dominance
-
Occurs when individuals have two B alleles or one B and
one O allele
-
Has B antigens on red blood cells
-
Blood produces anti-A antibodies
-
Can accept type B and AB blood
-
Can donate blood to type B and O individuals
-
Occurs when individuals have two O alleles
-
Has no antigens on red blood cells
-
Blood produces anti-A and anti-B antibodies
-
Can accept type O blood
-
Can donate to anybody

Rh- (43)
-
Individuals with this blood type do not have the Rh factor
expressed on the red blood cell surface

Rh+ (43)
-
Individuals with this blood type have the Rh factor
expressed on the red blood cell surface
APPLICATIONS OF GENETICS



ABO blood typing (42, 43,
49)
Agarose gel electrophoresis
(75, 76)
Amniocentesis (48)
-
Discovered by Karl Landsteiner
-
Most common form of blood typing
-
Used to identify phenotypes in paternity legal cases until
1984
-
Rejected as courtroom evidence in the 1943 Barry/Chaplin
case
-
Technique used to separate DNA fragments
-
Forms a pattern of DNA fragments unique to each
individual
-
Used in RFLP
-
One of two ways doctors can perform a karyotyping on a
fetus
-
Uses a needle to extract fetal cells within the fluid part of
the fetal membrane
Science Power Guide | 114

Biotechnology (71, 75)
-
Use of molecular biology to manufacture useful products,
improve human life and tackle environmental challenges

CVS (48)
-
Acronym for chorionic villus sampling
-
One of two ways doctors can perform a karyotyping on a
fetus
-
Doctors directly remove part of the fetal membrane
-
More invasive than amniocentesis

Epigenetics (5, 77, 81)
-
Study of chemical and environmental factors that affect
genes

Functional genomics (80)
-
Study of the biological functions of genes and gene
products
-
Investigates how DNA and proteins interact
-
Acronym for genetically modified organisms
-
Used to increase crop quality and production and facilitate
biomedical research
-
Can pose risks to human health, other species, and the
environment
-
Chromosomal analysis test
-
Can identify the genetic disorders of offspring in utero
-
Doctors extract fetal cells
-
Acronym for polymer chain reaction
-
Method of mass-producing DNA
-
One of the most commonly used molecular biology
procedures
-
Developed by Kary Mullis in the 1980s
-
Involves the three steps of denaturation, annealing, and
extension/elongation
-
Requires genomic DNA, primers, Taq polymerase, and four
types of nitrogenous bases
-
Used in RFLP



GMOs (76, 77)
Karyotyping (48)
PCR (73, 76, 79)

Pedigree (48)
-
Diagram that traces a phenotype over many generations

RFLP (75)
-
Acronym for restriction fragment length polymorphism
-
Standard law enforcement procedure for establishing
evidence needed to convict or exonerate criminal suspects
-
Also known as DNA fingerprinting
-
Involves PCR, restriction enzyme digestion, and agarose
gel electrophoresis
-
Used in paternity and maternity disputes
-
Used to identify individuals
Science Power Guide | 115

Transgene (77)
-
Gene transferred from one species to another through
recombinant DNA techniques
ORGANS203

Endometrium (44)
-
Inner epithelial lining of the uterus

Fallopian tubes (17)
-
Lined with ciliated204 cells

Kidneys (39)
-
Produces erythropoietin when blood oxygen levels are low

Ovaries (23, 26, 47)
-
Female reproductive organ

Pancreas (73)
-
Produces insulin in humans

Petiole (44)
-
Stalk that attaches the leaf to the plant stem

Placenta (44)
-
Organ found in pregnant female animals
-
Nourishes the fetus and eliminates fetal waste
-
Male reproductive organ
-
Gonadal germ cells mature into gametes in this organ
-
Also known as the windpipe
-
Lined with ciliated cells
-
Acronym for breast cancer 1 and breast cancer 2
-
Having this gene increases the risk of breast and ovarian
cancer
-
Found in less than one percent of humans
-
Causes less than 10% of breast cancer cases
-
Gene that stimulates cell proliferation
-
Cancer results when this gene mutates or activates
abnormally
-
Acronym for sex reversal Y
-
Activates the development of testes and other male
genitalia
-
If this gene is not present, female sex hormones activate
the production of ovaries


Testis (9, 23, 47)
Trachea (17)
GENES



203
204
BRCA1/BRCA2 (44)
Oncogene (28)
SRY (47)
Not just human organs, of course
Ciliated cells are cells that have cilia projecting from the cell body.
Science Power Guide | 116
LABORATORY TECHNIQUES



Centrifugation (58, 61)
Paper chromatography (58)
X-ray crystallography (58)
-
The process of spinning a sample around an axis at high
speed
-
Separates a sample’s contents based on size, density, and
weight
-
Used by Hershey/Chase and Meselson/Stahl
-
Separates and isolates substances in a mixture based on
their physical and chemical properties
-
Used by Edwin Chargaff
-
Uses X-rays to determine a crystallized molecule’s
shape205
-
Used by Rosalind Franklin
TIME PERIODS

10 hours (19)
-
Time required for one bacterium to produce 1 billion bacteria

20 minutes (19, 61, 62, 75)
-
Time required for a bacterium to produce two daughter cells

20 to 24 hours (20)
-
Time required for one complete cell cycle

Two months (47)
-
Length of human gestation before sex differentiation begins
205
In this technique, an X-ray beam is shot at a molecular crystal. The resulting diffraction pattern can be used to reconstruct the electron
density, allowing scientists to build a model of the molecular structure.
Science Power Guide | 117
The Development of Pre-Mendelian Genetics
5th century B.C.
Hippocrates develops the pangenesis theory
350 B.C.
Aristotle publishes History of Animals and Generation of Animals
1665
Robert Hooke publishes his observations of cells in Micrographia and uses the word “cell”
for the first time to describe the structure of cork
1674
Anton von Leeuwenhoek studies microbiological specimens through microscopes
1695
Nicolaas Hartsoeker illustrates “homunculus” in a sperm cell
1730s
Carolus Linneaus develops the first taxonomic system
1760s
Joseph Kolreuter is the first to systematically study genetic crosses (using tobacco plants)
1794
John Dalton describes red-green colorblindness
1809
Jean-Baptiste Lamarck proposes his theory of the inheritance of acquired traits
1831
Robert Brown is the first to describe and name the nucleus
1838
Matthias Schleiden theorizes that the nucleus plays a role in cellular reproduction
1838-39
Matthias Schleiden, Theodor Schwann, and Rudolf Virchow develop the cell theory
1858
Charles Darwin and Alfred Russel Wallace present their ideas on evolution by natural
selection to the Linnean Society of London
1859
Charles Darwin publishes On the Origin of Species by Means of Natural Selection
The Life of Gregor Mendel
Time
Event
1847
Mendel is ordained as a minister and begins work at a monastery in Brno
1854
Mendel begins his experiments with pea plants
1865
Mendel concludes his experiments with pea plants
1866
Mendel publishes Experiments on Plant Hybridization
1868
Mendel is elected to the position of prelate
1884
Mendel dies
Modern Genetics
1869
Friedrich Miescher discovers nucleic acid in white blood cells
1875
Robert Koch links microorganisms and infectious disease
1878
Walther Flemming observes and describes chromosomal behavior during mitosis
Science Power Guide | 118
1889
August Weismann proposes the germ-plasm theory of heredity
1889
Hugo de Vries theorizes that “pangenes” are responsible for passing traits from one
generation to the next
1900
Carl Correns, Hugo de Vries, and Erich von Tschermak independently rediscover and confirm
Mendel’s laws of inheritance
1900
Karl Landsteiner discovers the ABO blood typing system
1901
Albrecht Kossel identifies the five nucleotides in DNA and RNA
1902-03
Udny Yule and William Castle observe and analyze the constant allele frequency in nonevolving populations
1902
Archibald Garrod discovers the first genetic disease (alkaptonuria)
1902
Walter Sutton and Theodor Boveri propose the chromosome theory of inheritance after
observing chromosomal segregation during meiosis
1905
Konstantin Mereschkowki proposes the endosymbiosis theory
1905
Edmund Wilson discovers the arrangement of human sex chromosomes Wilson and Nettie
Stevens determine the differences between male and female sex chromosomes
1905
William Bateson discovers linked genes first uses the word “genetics”
1908
G.H. Hardy and Wilhelm Weinberg independently develop the Hardy-Weinberg theorem
1910-11
Thomas Hunt Morgan conducts his studies of fruit flies and proposes that certain traits are
linked to sex chromosomes confirms the chromosome theory of inheritance
1913
Alfred Sturtevant and Thomas Morgan create the first gene linkage map
1913
Estella Carothers provides cytological evidence of the independent assortment of
chromosomes through her observations of grasshopper testis
1918
R.A. Fisher, Sewall Wright, and J.B.S. Haldane launch the modern synthesis of evolution with
their work, “The Correlation between Relatives on the Supposition of Mendelian Genetics”
1919
Phoebus Levene identifies deoxyribose in DNA molecules
1928
Frederick Griffith conducts studies of virulent and non-virulent strains of bacteria and coins
the term “transforming principle”
1938
Theodosius Dobzhanksy unites genetics and evolutionary biology with his work “Genetics and
the Origin of Species”
1940
G. Ledyard Stebbins proposes polyploidy as a method of sympatric speciation
1942
Ernst Mayr proposes the “biological species concept”
1944
Oswald Avery, Colin MacLeod, and Maclyn McCarty demonstrate DNA as the genetic material
1950s
Werner Aber discovers restriction enzymes
1950
Erwin Chargaff proposes the base pairing rules that bear his name
1951
Rosalind Franklin uses X-ray diffraction to capture images of DNA molecules
Science Power Guide | 119
1952
Alfred Hershey and Martha Chase disprove the idea that proteins carried genetic material
1953
Francis Crick and James Watson discover the double helix structure of DNA
1953
Stanley Miller and Harold Urey demonstrate the formation of organic molecules from nonorganic molecules present on the early Earth
1958
Matthew Meselson and Frank Stahl prove the semiconservative model of DNA replication
1958
Arthur Kornberg and Severo Ochoa isolate DNA polymerase I from E. coli
1960s
Thomas Brock discovers thermophlic bacteria in Yellowstone National Park, which leads to the
discovery of Taq polymerase used in PCR
1985
Kary Mullis is the first to describe the polymerase chain reaction
1990206
The Human Genome Project begins
1999
Scientists sequence the cystic fibrosis gene
2003
The results of the Human Genome Project are published
RNA Molecules
rRNA
Nucleic acid that clusters with proteins to form ribosomes
mRNA
Nucleic acid that carries genetic information from the nucleus to ribosomes
tRNA
Nucleic acid that is involved in protein synthesis
ribozyme
Self-splicing nucleic acid; involved in protein synthesis and post-transcription RNA processing
miRNA
Leftover products spliced from mRNA after transcription; can defend against DNA/RNA
viruses and may be involved in cancer formation
siRNA
Leftover products after enzymes digest certain double-stranded RNA molecules
Equations
Hardy-Weinberg
equation
2  2  2  1
Multiplication
rule
      ∗ 
Addition rule
       
Binomial
theorem
206
   ∗     2  2  2
USAD states the HGP was launched in 1988 in the timeline, but that it “officially launched in October 1990” on page 78.
Science Power Guide | 120
Cell Basics
Characteristics of All Cells
Surrounded by a plasma
membrane
Produce carbohydrates,
lipids, proteins, and
nucleic acids
Contain genetic material
Contain subcellular
structures with distinct
functions
Domains of Life
Cell Theory
Eukarya
Bacteria
Archaea
Cells are the
basic units of
life
Eukaryotic
Kingdoms
Protista
Animalia
Plantae
Cells make up
all living
organisms
All cells come
from preexisting cells
Transportation
Recognition
Functions of
Protein
Molecules
Fungi
Signal transmission
Enzymatic reactions
Cell Organelles
Cytosol
Plasma
membrane
Nuclear
membrane
Microtubules
Subcellular
Organelles
Cytoplasm
Cytoplasm
Endoplasmi
c reticulum
Intermediate
Filaments
Eukaryotic
cell
Organelles
Golgi
apparatus
Vesicles
Endomembrane
system
Microfilaments
Cytoskeleton
Science Power Guide | 121
Microtubules
Act as the cell s skeletal system and
provide intracellular support
Transport molecules within the cell
Serve as spindle fibers during meiosis
Ease cellular movement by acting as cilia
and flagella
Largest of the cytoskeletal elements
Support and
maintain cell
shape
Ease cellular
movement
Roles of the
Cytoskeleton
Intermediate
Filaments
Microfilaments
Cage-like filaments
Stabilize and maintain the position of
organelles
Molecular configuration is similar to the
steel cables of suspension bridges
Resemble strings of beads
Provide strength, mobility, and shape to the
cell
Involved in phagocytosis (cell eating),
pinocytosis (cell drinking), muscle
contraction, and cell movement
Thinnest of the cytoskeletal elements
Anchor
internal
organelles
Cilia
Ease protein
transport
within the
cell
Interact with
extracellular
anchor
structures
Flagella
Small projections
from the cell's
surface
One or two tails
Used by cells in
the trachea and
fallopian tubes
Move by lashing
back and forth
Used by sperm
cells
Mitochondria
Mitochondria and
chloroplasts
Replicate
independently and
survive on their own
Found in animal cells
Chloroplast
Found in plant and
photosynthetic protist
cells
Contain their own
circular DNA separate
from the nucleus
Contain chlorophyll
Produce adenosine
triphosphate (ATP)
through cellular
metabolism
Contain prokaryotic-like
ribosomes
Enclosed by a doublelayered membrane
Transform solar energy
into ATP
Science Power Guide | 122
Support the cell
wall
Eliminate excess
water
Maintain cellular
rigidity
Central
Vacuole Jobs
Ensure balanced
levels of salt in
cytoplasm
Store wastes,
toxins, and
pigments
Cellular Reproduction
Tasks of subcellular organelles during cellular reproduction
DNA replication
Organelle duplication
Relocation of
duplicated organelles
Distribution of
duplicated organelles
Science Power Guide | 123
Binary Fission
DNA replication creates two DNA loops
The loops attach to the plasma membrane
The cell expands and elongates
The plasma membrane pinches and splits
Two identical daughter cells are formed
Simple cytoplasmic structure
Absence of membrane enclosing DNA
Single DNA molecule
Binary fission is
simple
Presence of multiple chromosomes
Presence of nuclear envelope surrounding
chromosomes
What makes eukaryotic cell division
complex?
Larger number of subcellular organelles
Creation of a new cell wall in some organisms
Methods of eukaryotic asexual reproduction
Fission
Mitosis
Regeneration
Budding
Science Power Guide | 124
‘
Chromatin condensation
Nucleoli disappearance
Cellular processes in meiosis prophase I
Nuclear envelope fragmentation
Nuclear
envelope
disappears
Spindle fibers
form and
attach to
kinetochores
Prophase II
Metaphase II
Sister
chromatids
align at the
metaphase
plate
Spindle fiber formation
Centromeres
split
Each
chromosome
towards the
poles
Anaphase II
Telophase II
Chromosomes
decondense
Nuclear
envelope
reforms
Cytoplasm
divides
Meiosis II ends
with four
haploid
daugher cells
Cytokinesis
Science Power Guide | 125
Early Prophase
Late Prophase
(Prometaphase)
Metaphase
Anaphase
Telophase
The dispersed sister chromatids condense
The nuclei disassembles
rRNA production stops
The centrosomes migrate towards the poles
Spindle microtubules from the microtubule organizing center push
away the two centrosomes
The nuclear envelope breaks into vesicles
Spindle microtubules interact with the chromosomes
Each sister chromatid builds a kinetochore near the centromere
The kinetochore microtubules separate the sister chromatids
Polar (or non-kinetochore) microtubules begin to elongate the
cell and push the centrosomes to the opposite ends of the cell
All chromosomes line up in the metaphase plate in the middle
of the cell
The kinetochore microtubules pull the sister chromatids
towards the cell's center
Polar microtubules continue to elongate the cell
"Adhesive proteins bonding the sister chromatids turn off
The centromere splits in two, and the chromatids are now two
individual chromosomes
The kinetochore microtubules pull the chromosomes towards
the poles
Polar microtubules continue to elongate the cell
The cell seeks to return to equilibrium
Chromosomes unwind and disperse
The nucleolus and nuclear envelope reassembles
The spindle microtubules and centrosomes break down
Science Power Guide | 126
Mutations
Silent
One nucleotide
substitutes for
another
The codon codes
for the same
amino acid
Missense
Nucleotide
substitution
changes the coded
amino acid
Nonsense
Frameshift
Nucleotide
substitution
produce a stop
codon
One nucleotide is
added or deleted
All subsequent
codons are
affected
Science Power Guide | 127
Types of
mutations
Translocation
Inversion
Substitution
Addition
Deletion
Types of Cells
Science Power Guide | 128
Dividing cells
Non-dividing cells
Skin cells
Nerve cells in the brain
Intestinal epithelial cells
Hair cells in the ear
Uterine endometrial cells
Heart muscle cells
Reproductively dormant
cells
Liver cells
Lens cells in the eye
The Cell Cycle
G1 phase
G2 phase
M phase
Cell Size
Cell size
Nutrient
availability
Spindle fiber
attachment to
chromosomes
Growth
DNA replication
DNA damage
Science Power Guide | 129
Mendel's Experiments
Pod shape
Easy to grow
Reproduce quickly
Flower color
Pod color
Why pea plants?
Flower position
Easy to manipulate
pollination
Easy to describe and
distinguish traits
Plant height
Pea shape
Pea Plant
Traits
Multiplication Rule
If two events are independent, then the probability that
they both occur is the product of the probabilities of each
occurring
•     ∗ 
Addition Rule
If two events are mutually exclusive, then the probability
of either event occuring is the sum of the individual
probabilities
•    
Binomial Theorem
•    ∗       2   
Pea color
Science Power Guide | 130
Mendelian Genetics
Two main categories of chromosomes
Non-sex chromosomes (autosomes)
Sex chromosome
Chromosomes 1-22
Chromosome 23
During gamete
formation...
Homologous
chromosomes
separate during
anaphase I
Alleles are split
Spem and egg cells
become haploid
Genetic Diseases
Cystic
fibrosis
A gene that codes for a channel protein on the cell surface mutates
The protein channel ceases to function
Thick and sticky mucus lines the lungs and digestive system
Lung infections and digestive problems result
Science Power Guide | 131
Point mutation occurs
Sickle
cell
anemia
TaySachs
disease
Protein in the hemoglobin molecule folds incorrectly
Red blood cell distorted from a donut into a sickle shape
Red blood cells can no longer squeeze th rough capillaries
Lack of oxygen leads to multiple organ failure
Single gene mutation alters a lipid metabolism enzyme
Abnormal lipid coats surround brain cells
The brain cannot transmit neural impulses correctly
Paralysis, blindness, and deafness can result
Diversity in the Pattern of Inheritance
Blood
Type
A
B
AB
O
Possible
Genotype
AA or AO
BB or BO
AB
OO
Antigens in
Red Blood Cell
A
B
A and B
None
Temperature
Antibodies
in Serum
Anti-B
Anti-A
None
Anti-A and
Anti-B
Social Structure
Environmental
Chemicals
Genetics
Factors that influence
an embryo's gender
207
Can Donate
Blood To
A, AB
B, AB
AB
A, B, AB, O207
This is why people with type O blood are known as “universal donors”
Can Receive
Blood From
A, O
B, O
AB, O
O
Science Power Guide | 132
Evolution
PreDarwinian
Theories
of
Evolution
Excess offspring in each
generation
Pangenesis
Natural selection of
favorable variations
Descent with
modification
Blending Inheritance
Darwin's
Theory
Lamarck's theory
Characteristics of a Non-Evolving Population
Characteristics of a Non-Evolving Population
Few physical
mutations
Large population
No migration or
random events
Equal
reproductive
success
Random mating
Large
population
No migration
Conditions for
Hardy-Weinberg
equilibrium
No natural
selection
No new
mutations
Random
mating
The Hardy-Weinberg Equation
      208
Term
What does it describe?


the frequency of the homozygous dominant phenotype

the frequency of the heterozygous dominant phenotype

208
the frequency of the homozygous recessive phenotype
Look familiar? The Hardy-Weinberg equation is identical to the one Mendel used to find the genotype ratio of his pea plants.
Science Power Guide | 133
defined evolution as a change in allele frequency within a
gene pool
suggested that mutation was the main force behind
evolution by natural selection
Dobshansky helped
shape the modern
synthesis of evolution
Produce
both male
and female
offspring
Ernst
Mayr's
definition
of a species
Offspring
are viable
and fertile
Population
migration
Natural selection
Non-random
mating
Genetic Drift
Causes of
Evolution
Genetic Material
Phosphate
Adenine
Cytosine
Components of
DNA
Nitrogenous Bases in
Nucleic Acid
Thymine
Pentose sugar
Guanine
Four nitrogenous
bases
Genetic Code
A
T
G
C
Science Power Guide | 134
Conservative
replication
The new DNA molecule consists of two
new strands
Semi-conservative
replication
Dispersive
replication
The new DNA molecule consists of one old
and one new strand
The new DNA moelcule consists of a mix
of old and new strands
Enzymes involves in DNA Replication
Helicase
Acts as an unzipper
Initiates DNA replication by unwinding the double helix
Forms a replication fork and bubble
Primase
Synthesizes new RNA primers
Atttaches these RNA primers to the replicating strands of DNA
DNA polymerase
Nuclease
DNA ligase
Serves as builder and proofreader
Continually adds complementary nucleotides to the daugher DNA
moelcule
Acts as an editor
Removes incorrect nucleotides
Acts as a zipper
Fills in holes in the new DNA molecule backbone with phosphate
Science Power Guide | 135
The RNA
primase
attaches to the
end of the DNA
strand
Helicase unzips
the parent DNA
molecule
DNA primase
synthesizes an
RNA primase
enzyme
DNa
fragments
replace the
RNA primase
DNA polymerase
synthesizes the
complementary
strand of DNA
DNA ligase "rezips"
the new DNA
fragment to the
parent
DNA
RNA
Double stranded
Single stranded
Deoxyribose
backbone
Ribose backbone
Larger in size
Has roles in many
cellular functions
Only role is to
store genetic info
Smaller in size
RNA
rRNA
Stands for ribosomal RNA
Made in the nucloeolus
Combines with proteins to form ribosomes
mRNA
Stands for messenger RNA
Produced by DNA transcription
Carries genetic information to the ribosomses for translation
tRNA
Stands for transfer RNA
Carries a specific amino acid
Complements the nucleotides in mRNA
Science Power Guide | 136
Three Phrases of Transcription
Initiation
RNA polymerase binds the promoter region
Elongation
Nucleotides are added to the RNA strand
Termination
The RNA strand separates from the DNA template once it reaches a termination factor
Three phases of translation
Initiation
Elongation
Termination
mRNA binds to a small ribosomal subunit
The first tRNA carrying methionine binds to the start codon on the mRNA
A large ribosomal subnit binds to the smaller to create a P site
The tRNA can then "dock" at this site
The next tRNA docks at the A site
The new amino acid forms a peptide bond with the first amino acid
The first tRNA exits the ribosome
The second tRNA moves from the A site to the P site, allowing the next tRNA to enter
The translation process ends when a stop codon is encounters
The peptide chain detaches from the ribosome
The ribosomal complex disassembles
Science Power Guide | 137
Modern Molecular Genetics
Science Power Guide | 138
Polymerase Chain Reaction
Denaturation
The starting reaction mixture includes genomic DNA, primers, and the four types of nucleotides
This mixture is heated to 95° C
The hydrogen bonds break, separating the two strands of DNA
Annealing
The mixture is cooled to between 50° and 60°C
The primers bind to their respective complementary sequences on the individual DNA strands
Extension (Elongation)
The mixture is heated to between 72° and 80°C (the optimal temperature for Taq polymerase)
The polymerase is added to the mixture
Primers initiate the continued addition of nucleotides to the DNA strands
Agarose gel is placed in a
electric field with a buffer
The restriction-digested DNA
fragments are placed in a well
DNA migrates towards the
positive pole of the electric field
A ladder pattern of DNA bands
form
Science Power Guide | 139
PRACTICE TEST ANALYSIS
To benefit the most from this analysis, please make sure that you’ve taken the USAD Science Practice test before
you proceed. The following will be a section-by-section breakdown of the test.
The cell cycle, the cell cycle, the cell cycle. USAD really drives home the process of cellular reproduction when
testing knowledge from Section I. It’s important to know the key events that occur during each phase of the cell
cycle—the subject of questions 2, 3, 20, and 49. These are simple recall questions that you should know and
expect to be tested on at all levels of competition. Section I questions also examine key contrasts between plant
and animal cells (question 4) and between prokaryotes and eukaryotes (questions 9 and 31). Be on the lookout
for places in the resource guide where USAD emphasizes the similarities and differences in structure and processes
of two different types of cells. In general, section I questions strike a balance between testing the big ideas and the
specifics, with no question standing out as especially difficult.
As expected, Section II tests the basic concepts of genetics, especially the different patterns of inheritance and key
terms (homozygous and heterozygous, dominant and recessive, among others). Be able to link these patterns of
inheritance with the examples USAD gives in the resource guide (co-dominance and ABO blood typing were
tested in two separate questions, for instance). Many of these questions are a paragraph long, describing real-world
context (questions 25, 30, 46, 47). Don’t let the specific details of the paragraph confuse you—just pay attention
to what the question is asking for, which is usually a basic principle of Mendelian genetics. Other questions only
ask for a definition (questions 34 and 41). Question 8 is one of the trickier Section II questions, as answer choice
(e) immediately draws the attention of most Decathletes. However, remember that humans have 22 autosomes
plus a pair of sex chromosomes (XX or XY), making (d) the correct answer. Question 16 is another stumper, as
USAD does not explicitly state the correct answer in the resource guide. You can, however, deduce the correct
answer by recalling that women have two X chromosomes and men have one X and one Y chromosome. The
mom has to provide an X chromosome to the baby, so it’s up to the dad to provide either an X (making the baby
a girl) or a Y (making the baby a boy). Fully understanding Section II is vital to scoring high on this year’s science
test—it’s the common thread that links all three of the sections together.
Questions on Section III emphasized DNA, RNA, and applications of genetics, with questions covering
epigenetics, GMOs, and various characteristics about DNA and RNA. The Hardy-Weinberg theorem and
equation appear to be important topics, as USAD devoted questions 11 and 12 to them. Questions about types
of mutations could be especially tough, as they are pure memory-based questions—make sure to emphasize
remembering the differences between these types in the days leading up to the competition. The Practice Test
noticeably neglected the numerous scientists that were involved in the modern evolutionary synthesis and the
discovery of DNA (except question 37, which tested Watson and Crick as the discoverers of DNA’s double helix
model)—expect to see more of these questions at the actual competition.
Overall, the USAD Science Practice Test seemed to emphasize knowledge recall much more than critical thinking
or synthesis of concepts. I expect to see fewer such questions on future tests, with more compare/contrast questions
(DNA and RNA, anyone?), problem-solving questions that ask you to draw Punnett squares and find certain
probabilities, and questions about the various geneticists and other scientists, especially the post-Mendel ones.
Without doubt, USAD makes clear that there are several key subject areas that you need to know forwards,
backwards, and upside-down. These include cellular structures and the cell cycle, the basic principles of Mendelian
genetics, including Mendel’s three laws, and the list of genetics terms found on page 33 of the Resource Guide.
Science Power Guide | 140
Q#
Topic
USAD
PAGE #
Q#
Topic
USAD
PAGE #
1
Mitosis
20
26
Applications of
genetics
77
2
Cell cycle
20
27
Inheritance patterns
42
3
Mitosis
21
28
Inheritance patterns
43
4
Mitosis
22
29
Cell structure
11
5
Meiosis
25
30
Applications of
genetics
76
6
Applications of
genetics
40
31
Cell structure
15
7
Mendelian genetics
33
32
Cell structure
18
8
Human genome
33
33
Mendelian genetics
33
9
Cell structure
13
34
Mendelian genetics
31
10
Modern synthesis
52
35
Mendelian genetics
36
11
Modern synthesis
53
36
Mendelian genetics
33
12
Mendelian genetics
32
37
DNA
60
13
Mendelian genetics
31
38
Protein synthesis
60
14
DNA
58
39
Protein synthesis
69
15
Human genome
33
40
Cell cycle
20
16
Human genome
47
41
Mendelian genetics
31
17
Human genome
47
42
Inheritance patterns
40
18
Human genome
76
43
Protein synthesis
68
19
Inheritance patterns
41
44
Mutations
64
20
Meiosis
27
45
Mendelian genetics
33
21
DNA
55
46
Mendelian genetics
39
22
Applications of
genetics
48
47
Mutations
64
23
Mendelian genetics
34
48
Protein synthesis
67
24
Modern synthesis
51
49
Protein synthesis
67
25
Applications of
genetics
77
50
RNA
65
Science Power Guide | 141
ABOUT THE AUTHOR
Eric Yang fits the typical Honors decathlete mold quite well.
Well, maybe not so much.
He joined Academic Decathlon as a freshman after he came to the
difficult realization that he wasn’t quite up-to-par while competing
the track-and-field decathlon. Ever since then, he’s been hooked by
the combination of late-night discussions on The Grapes of Wrath,
debates about the impact of European imperialism, and the
consumption of ramen noodles out of a coffee maker. This year, Eric
will be a senior at The Colony High School, hoping to bring lasting
glory and fame to his AcDec team and school once and for all.
His Honors mentality extends to the rest of his lifestyle, where he
meticulously keeps a multicolored pen and half a dozen sharpened
pencils with him at all times, he uses the philosophy of Locke and Hobbes to argue about the relative merits
of school lunch, and he constantly plays Civilization IV in order to prove that the Ottoman Empire could
have (and should have) conquered Vienna in 1683, quite possibly changing the fate of Western civilization
forever.
He has spent nearly his whole life in the Dallas suburb of The Colony. Though he desires to see the world,
deep down inside he misses sweet tea, 100+ degrees summer weather, and the frequent use of “y’all” that
were a part of his childhood.
When he’s not persuading his friends to become fellow Decathletes or conducting science experiments (i.e.
tossing lithium into local waterways), Eric can be found watching The Big Bang Theory or Arrested
Development, doing Pilates in an effort to improve his infamous inflexibility, and playing jazz piano. You
usually won’t be able to find him at home, though, as he has a slight obsession with hiking and mountain
biking (though in one embarrassing incident he did sprain his ankle by just getting off a bike).
Eric hopes to become the next Ms. Frizzle of Magic School Bus (or, as in the above photo, its lesser-known
4WD cousin, the Magic School Jeep) fame, sharing his passion for science with his next-door neighbor, the
barista at the local coffee shop, and the Tibetan yak-herder halfway around the world.
If you would like more random biographical facts, need a lab partner for that ever-so-challenging organic
chemistry class, or simply have a good science joke to share, feel free to contact Eric at
[email protected].
Vital Stats




209
Competed with The Colony High School at the Region and State competitions in 2011-13
Earned the highest score at the 2013 Texas Medium School State competition with 8,893.3 points209
Decathlon philosophy in a phrase: “It’s not just any competition. It’s a way of life.”
Joined DemiDec in May 2011
Yes, those three-tenths of a point are oh-so important.
Science Power Guide | 142
ABOUT THE EDITOR
Josephine Richstad is the Editorial Director at DemiDec. She competed in
Academic Decathlon exactly once in her hometown of Columbia, South Carolina
and does not remember what her score was, although she does remember that it
was the highest in the state—out of both competing high schools.
After this pinnacle of academic achievement, she earned a BA in English with
honors from Columbia University and a Ph.D. in English from UCLA. Her
published writing ranges from Writing Everyday English Emails to “Genre in
Amber: Preserving the Fashionable Novel for a Victorian Decade, Catherine
Gore’s Hamiltons (1830 and 1848)” (Modern Philology, February 2014). She
wrote her first DemiDec resource in 2008 and is currently deciding to which
position she'll promote herself next year.
Josephine now lives in the bucolic college town of Ithaca, New York where she’s earning her Ph.T. at Cornell
Law School. She has a dog, a cat, and a three-year-old daughter, who nearly decapitated a rather large stuffed
alpaca at the 2012 World Scholar's Cup Tournament of Champions.
She is very sorry.
When Josephine is not checking her DemiDec email at 3 in the morning, she can be found making jam,
knitting, watching BBC procedurals, and losing at Dominion. To discuss AlpacaGate, college towns,
nineteenth-century novels, or Dominion strategies, you can contact her at [email protected]. You can
also follow her on Twitter @jrichstad, where she currently averages eight tweets per year.