Download Keystone Study Guide Module B: Continuity and Unity of Life

Keystone Study Guide Module B: Continuity and Unity of Life
Topic 5: Cell Growth and Reproduction
Cellular Growth
Cells grow until they reach their size limit, then they either stop growing or divide.
Size is limited by the need to (1) transport items within the cell and (2) communicate within the cell
Unicellular organisms use mitotic cell division for reproduction
Multicellular organisms use mitotic cell division for development of the embryo, growth, and repair
The Cell Cycle
1. Interphase – the cell is growing and DNA replication occurs
2. Mitosis – the cell’s nuclear material is equally divided
3. Cytokinesis – the cell’s cytoplasm and remaining contents are divided
a. A cleavage furrow divides animal cells
b. A cell plate divides plant cells
The cell cycle is regulated by cyclins; disruption of the cell cycle can result in uncontrolled growth (cancer)
Mitosis
1.
2.
3.
4.
Prophase – chromatin condenses to chromosomes; nuclear membrane dissolves; spindle forms
Metaphase – chromosomes align at the cell’s equator with help from the spindle
Anaphase – sister chromatids move to opposite poles
Telophase – chromosomes reach the poles; nuclear membrane reappears; spindle dissolves
Meiosis (also called Reduction Division)
Meiosis produces haploid gametes (sex cells), which pass on genetic information
1. Interphase – the cell is growing and DNA replication occurs
2. Meiosis I
a. Prophase I – nuclear envelope dissolves; chromosomes condense; spindle forms; crossing over
during synapsis (exchange of genetic information between homologous chromosomes)
b. Metaphase I – Homologous chromosomes align at the equator
c. Anaphase I – Homologous chromosomes separate and move to opposite poles
d. Telophase I – Chromosomes reach poles and decondense; two nuclei form; spindle breaks down
3. Meiosis II
a. Prophase II – Chromosomes decondense; spindle forms
b. Metaphase II – Chromosomes align randomly at the equator
c. Anaphase II – Sister chromatids separate and move to opposite poles
d. Telophase II – Chromosomes reach poles and decondense; four nuclei form ; spindle breaks down
Comparing and Contrasting Mitosis and Meiosis
Mitosis
Meiosis
One nuclear division
Two nuclear divisions
Results in two genetically identical daughter cells
Results in four genetically unique daughter cells
Involved in growth and repair
Involved in gamete production
DNA replication occurs in Interphase
Involves the division of the cell’s nucleus
Reproduction
Asexual reproduction involves one parent and produces identical offspring (examples: bacteria, yeast)
Sexual reproduction involves two parents and produces unique offspring (example: humans)
2
Chromosomes
Chromosomes are made up of DNA and DNA is made up of genes, which are units of heredity
In terms of n, haploid cells have n number of chromosomes
In humans, the sperm and egg are haploid cells and each has 23 chromosomes
In terms of n, diploid cells have 2n number of chromosomes
In humans, the body cells (somatic cells) are diploid and each has 46 chromosomes
Homologous chromosomes
Same length
Same centromere position
Carry similar genes for same inherited traits
Topic 6: Genetics
Important Vocabulary
Gene –segment of DNA that makes up a chromosome; the unit of heredity
Locus – location of a gene on a chromosome
Allele – alternative form of a single gene (always exist in pairs)
Dominant – form of the trait that is expressed; represented by capital letter (P)
Recessive – form of the trait that is hidden; represented by lowercase letter (p)
Homozygous – an organism with two of the same alleles
Homozygous dominant – both alleles are dominant (PP)
Homozygous recessive – both alleles are recessive (pp)
Heterozygous – an organism with two different alleles (Pp)
Genotype – an organism’s genetic make-up of alleles pairs (PP, Pp, pp)
Phenotype – an organism’s physical appearance (purple-flowered or white-flowered)
Genetic recombination – new combination of genes produced through crossing over and independent
assortment
Gregor Mendel (“the Father of Genetics”)




Austrian monk and “citizen scientist”
Established inheritance pattern of specific traits (heredity) in pea plants
o Performed crosses between true-breeding pea plants; P (parent) generation
o Heterozygous (hybrid) offspring all had dominant trait; F1 (1st filial) generation
o Monohybrid cross offspring had 3:1 phenotypic ratio; F2 (2nd filial) generation
Law of Segregation – separation of alleles ensures offspring acquire one allele from each parent
Law of Independent Assortment – allele pairs separate independently in gamete formation
o Linked genes – two alleles located together on a chromosome usually inherited together; an
exception to Independent Assortment
Punnett Squares, Crosses, and Basic Probability






Punnett squares predict the result of genetic crosses between organisms of known genotypes
BE ABLE TO PERFORM PUNNETT SQUARES!
Monohybrid cross – involves single trait (flower color, pea pod shape, etc.)
Dihybrid cross – involves two traits (pea pod shape and color, etc.)
Testcross – mating used to determine genotype of an organism with dominant phenotype
Use Punnett squares to make calculating probability easier!
3
Chromosomes
The first 22 chromosome pairs in humans are called autosomes
Traits carried on autosomes are autosomal
Autosomal recessive genetic disorders
o Individual is homozygous recessive for the trait
o Carriers are heterozygous for the trait
o Examples: Cystic fibrosis, albinism, Tay-Sachs disease
Autosomal dominant genetic disorders
o Individual is homozygous dominant or heterozygous for the trait
o No carriers
o Examples: Achondroplasia, Huntington’s Disease
The last pair of chromosomes in humans are called sex chromosomes
In humans, XX = female and XY = male
o Egg contributes X chromosome
o Sperm contributes X or Y chromosome
Traits carried on sex chromosomes are called sex-linked or “X-linked”
o Autosomal recessive sex-linked traits
 More common in males, who only have one X chromosome
 Examples: Red-green color blindness, hemophilia
Pedigrees are used to study inheritance of a trait over several generations
Incomplete Dominance, Codominance, and Multiple Alleles
Incomplete dominance is when heterozygous phenotype is intermediate between two dominant phenotypes
(“blending”)
 Example: Red flower + White flower = Pink flower
Codominance is when heterozygous phenotype expressed both alleles
 Example: Red flower + White flower = Red and white flower
Multiple alleles is when traits are determined by more than two alleles
 Example: ABO blood group in humans
Polygenic traits arise from interaction of multiple pairs of genes
 Examples: Skin color, eye color
Environment can influence the phenotype of an organism
o Example: Diet/exercise affects risk of heart
disease, seasons affect animal coat color
Chromosomal Disorders
Karyotypes are pictures of pairs of homologous chromosomes
from humans
 Used to diagnose chromosomal disorders
o Example: Nondisjunction is the incorrect division
of sister chromatids, resulting in monosomy or
trisomy (Trisomy 21 is also known as Down
Syndrome)
 Fetal testing like amniocentesis and fetal blood sampling are used to generate karyotypes
4
History of DNA Research




Hershey and Chase – used viruses to prove DNA is the genetic material
Chargaff – observed that A = T and G = C in all species
Franklin – took pictures of DNA showing the shape is a double helix
Watson and Crick – proposed the structure of DNA; won the Nobel Prize in 1962
DNA


Nucleic acid made of nucleotides
DNA has two complementary
strands running in anti-parallel
directions
o Outside rails made of sugar
and phosphates
o Inner rungs made of nitrogen
bases
 Bases in DNA (A, T,
G, and C – A pairs
with T and G pairs
with C)
 Bases carry the genetic information
Copying DNA is called replication
Called semi-conservative: each parent strand
serves as template for new DNA
Occurs in nucleus in eukaryotes and cytoplasm
in prokaryotes
Enzyme that unwinds DNA is DNA helicase
Enzyme that builds the new DNA strand is DNA
polymerase
Enzyme that adds RNA primer to each DNA
strand is RNA primase
Enzyme that links sections of DNA together is
calledDNA ligase
BE ABLE TO WRITE DNA COMPLEMENTS OF GIVEN DNA STRANDS
RNA




Making RNA from DNA template is called
transcription
Nucleic acid made of nucleotides
Different from DNA:
o DNA is double helix, RNA is single
helix
o DNA has deoxyribose sugar; RNA has
ribose sugar
o DNA has bases A, T, G, C; RNA has
bases A, U, G, C (uracil replaces thymine)
Three types: rRNA (forms the ribosome), tRNA (transports amino acids); mRNA (messenger)
BE ABLE TO WRITE RNA COMPLEMENTS OF GIVEN DNA STRANDS
5
Protein




Making protein from RNA is called
translation
Protein synthesis is carried out by the
ribosome
Three-base code in mRNA is the codon
BE ABLE TO USE CODON CHART TO
WRITE AMINO ACIDS OF GIVEN RNA
STRANDS
DNA Tools




Restriction enzymes are found in bacteria
as a defense against viruses
o Digest the sugar-phosphate backbone of DNA
o BE ABLE TO DRAW HOW RESTRICTION ENZYMES CUT DNA
DNA ligase is used to seal pieces of DNA that have complementary ends
Fragments of DNA are separated using gel electrophoresis
o Separates based on size of DNA using electricity
o DNA is negatively-charged because of the sugar-phosphate backbone
o BE ABLE TO USE GEL ELECTROPHORESIS DATA TO ANSWER QUESTIONS
DNA fingerprinting is used in forensic science, paternity, and the identification of remains
Selective Breeding

Organisms are chosen to reproduce based on a desired trait
o Dogs have been bred for specific breeds (small/large, long hair/short hair, etc.)
o Fruits/vegetables have been bred for size and taste
Gene Splicing and Genetically Modified Organisms


In gene splicing, DNA is cut apart and recombined in different ways
o Same restriction enzyme should be used on each piece of DNA so ends are the same
A genetically modified organism (GMO) is created by inserted a gene from one organism into
another organism.
o Benefits include crops that are better tasting, more nutritious, and hardier
o Risks include contamination of organic farms and increased resistance to pesticides
Gene Therapy


Changes DNA of a person with a genetic disease by introducing working genes into cell nuclei
o Viruses used as the delivery mechanism
Genetic diseases caused by a single gene are good candidates
Cloning



Process of creating an organism that is genetically identical to another organism
Steps include: isolating donor somatic cells, removing the nucleus from an egg cell, inserting the
nucleus from donor somatic cells, and implanting the embryo into a surrogate mother
Natural clones include identical twins and asexually reproducing organisms, such as bacteria, yeast,
some plants, and some reptiles
6
Topic 7: Theory of Evolution
The Theory of Evolution by Natural Selection


Developed by Charles Darwin after observing finches on the Galapagos Islands
o Hypothesized nature could change species just as humans bred pigeons
o Reasoned some would be equipped to survive; those not equipped would die
Natural selection is the mechanism by which evolution occurs
o Four principles:
 Variation – individuals in a population differ from one another
 Heritability – variations are inherited from parents
 Overproduction – populations produce more offspring than can survive
 Reproductive advantage –variations allow organisms to have more offspring
o Four types of natural selection:
 Stabilizing selection – eliminates extremes in favor of the average
 Directional selection – eliminates one extreme in favor of the other
 Disruptive (diversifying) selection – eliminates average in favor of extremes
 Sexual selection – changes traits (often in males) based on ability to mate
Adaptations are traits shaped by natural selection to increase organism’s fitness (reproductive
success)
 Mimicry – species can resemble another species
 Camouflage – species can blend into their environments
Evolution is any change in a heritable trait within a population across generations
o

Mechanisms of Evolution




A population is a group of organisms of the same species that live together and interbreed
Allele frequency refers to how commonly an allele occurs in a population
o Change in frequency due to chance is genetic drift
 The founder effect is an extreme example of genetic drift
 Migration is movement of individuals and alleles into or out of a population
Divergent evolution occurs when a population evolves into a new species
o The formation of a new, genetically distinct species is speciation
o Isolating mechanisms are barriers preventing interbreeding between different species
 Pre-zygotic isolation operates before fertilization occurs
 Post-zygotic isolation operates after fertilization occurs
 Geographic isolation physically divides two populations through a barrier
Convergent evolution occurs when two unrelated species evolve similar adaptations (sharks and
dolphins both evolved similar body shapes independently)
7
Evidence of Evolution
EMBROLOGY compares the embryos of
different species. The similar development
patterns of the species above indicates that
they shared a common ancestor
FOSSIL EVIDENCE links present day organisms to
the common ancestors. Here we see the bones of
modern horses (top) and how much it has changed
from common ancestors (bottom)
HOMOLOGOUS STRUCTURES are structures that have the
same shape/form, but are used differently. The bones in the
center are from the common ancestor, but each species has
evolved to use them differently
BIOCHEMICAL EVIDENCE compares the differences in
either DNA or proteins (in this case, proteins. The lamprey
has the most differences from humans, which indicates we
diverged from the lampreys (are less related) much longer
ago than the macaques (more related)
Not shown are vestigial structures, which are structures reduced in size that are no longer needed but were
present in a common ancestor. Also not shown are analogous structures, which are structures that look the
same but are made out of different materials.
8
Topic 8: Ecology
Ecology is the study of how organisms
interact with their environment. There are
many different levels of ecology. The
diagram to the left shows all of the
different levels
Ecosystems have both living components (biotic factors such as the trees,
birds, and fish) and nonliving components (abiotic factors such as how
much rain or sun an area gets). All ecosystems need energy, and the most
basic form of energy comes from the sun. Producers (also known as
autotrophs) are able to make their own food. These are eaten by
consumers (also known as heterotrophs). We can track the flow of energy
linearly using a food chain or look at a more detailed flow of energy using a
food web.
Organisms can interact with each other in many different ways.
Symbiosis is the general term for organisms that closely
interact with each other. There are three different types of
Symbiosis: parasitism, mutualism, and commensalism. The
table to the right shows some of the different ways different
organisms can interact with each other.
A limiting factor is some sort of factor (biotic or abiotic) that is going to limit the population’s growth.
It could be an important nutrient that is cycled through the ecosystem (such as water, nitrogen,
carbon, or phosphorus), or it could be a food source or predator. A great example of limiting factors
are predator-prey graphs. It is easy to see how the size
of the population is affected.
Here, the size of the populations depends on the number or prey
and predators. The predator population peaks after the prey
population because of the lag time in reproduction. When the
predator population is at its highest, the prey is at its lowest. With
limited food, the population size of the predator decreases. This
allows the prey population to increase, and the cycle continues
again…
9
Nutrient Cycles
Important nutrients such as carbon, nitrogen, phosphorus, and water are cycled through living things and the
environment through biogeochemical cycles. The following pictures are overviews of the carbon,
phosphorus, and nitrogen cycles.
Carbon Cycle
Nitrogen Cycle
These natural processes are affected by human involvement. The table below shows how humans
change the cycles:
Cycle Disturbance/problem
Ecosystem Effect
Hydrologic /deforestation
and paving
 evapotranspiration, runoff,  erosion,  flooding
Carbon/fossil fuel
combustion and
deforestation
 CO2 levels,  atmospheric heat retention,  global warming
Nitrogen/excess (fertilizers,
pig farms)
 Atmospheric N2, change of diversity (eutrophication)
Phosphorus/excess
(fertilizers, detergents,
bird/bat guano)
Algal bloom, change of diversity
Eutrophication is a term that demonstrates how changing nutrient
levels affect the organisms in an ecosystem. For eutrophication, and
increase of nutrients (usually nitrogen and phosphorus because they
are limiting nutrients) is added. This increases photosynthesis
(sometimes called an algal bloom because the algae covers the top of
the body of water), and as these producers die, the decomposers come
in to feed off of them. These decomposers are going through
respiration and lower the oxygen available to all organisms that can
cause many to die.
10
Biology Keystone Module B Review Questions:
1. Describe the events that occur during the cell cycle: interphase, nuclear division (i.e., mitosis or
meiosis), cytokinesis.
2. Compare and contrast the processes and outcomes of mitotic and meiotic nuclear divisions.
3. Describe and/or predict observed patterns of inheritance (i.e., dominant, recessive, co-dominance,
incomplete dominance, sex-linked, polygenic, and multiple alleles).
4. Describe processes that can alter composition or number of chromosomes (i.e., crossing-over,
nondisjunction, duplication, translocation, deletion, insertion, and inversion).
5. Describe how the DNA replication results in transmission and/or conservation of genetic information.
6. Explain functional relationships among DNA, genes, alleles, and chromosomes and roles in inheritance.
7. Describe how the processes of transcription and translation are similar in all organisms.
8. Describe the role of ribosomes, endoplasmic reticulum, Golgi apparatus, and the nucleus in the
production of specific types of proteins.
9. Describe how genetic mutations alter the DNA sequence and may or may not affect phenotype (e.g.,
silent, nonsense, frame-shift).
10. Explain how genetic engineering has impacted the fields of medicine, forensics, and agriculture (e.g.,
selective breeding, gene splicing, cloning, genetically modified organisms, gene therapy).
11. Explain how natural selection can impact allele frequencies of a population.
12. Describe the factors that can contribute to the development of new species (e.g., isolating mechanisms,
genetic drift, founder effect, migration).
13. Explain how genetic mutations may result in genotypic and phenotypic variations within a population.
14. Interpret evidence supporting the theory of evolution (i.e., fossil, anatomical, physiological,
embryological, biochemical, and universal genetic code).
15. Distinguish among scientific terms: hypothesis, inference, law, theory, principle, fact, and observation.
16. Describe levels of organization (i.e., organism, population, community, ecosystem, biome, biosphere).
17. Describe characteristic biotic and abiotic components of aquatic and terrestrial ecosystems.
18. Describe how energy flows through an ecosystem (e.g., food chains, food webs, energy pyramids).
19. Describe biotic interactions in an ecosystem (e.g., competition, predation, symbiosis).
20. Describe how matter recycles (i.e., water cycle, carbon cycle, oxygen cycle, nitrogen cycle).
21. Describe how ecosystems change in response to natural and human disturbances (e.g., climate
changes, introduction of nonnative species, pollution, fires).
22. Describe the effects of limiting factors on population dynamics and potential species extinction.
11