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Semester 1 Final Exam Review
2012
ACCELERATED BIOLOGY
Unit 1
SCIENTIFIC METHOD AND BIOCHEMISTRY
CHAPTER 1 (OMIT 1:2)
CHAPTER 2
1. What are the 7 characteristics of life? Describe each and give an example
of an organism and how it exhibits that characteristic.
1.
2.
3.
4.
5.
6.
7.
Cellular Organization – Made of 1 or more cells. Ex) A Bacterium is 1
cell and humans are composed of trillions of cells.
Reproduction – Sexual or asexual. Organisms make more of their
own kind
Metabolism – Sum of all the chemical reactions carried out by an
organism in order to obtain and use energy.
Homeostasis – Maintain a stable internal environment.
Heredity – Pass on traits to their offspring. Ex) children resemble
their parents
Responsiveness – Responding and adjusting to the environment.
Growth and development – Pass through stages of development. Ex)
Tadpole  frog
2. Describe the parts of the Scientific Method.
Observation – Using your senses to study the world.
Problem – Asking a narrow question based on specific observations.
Hypothesis – Educated guess to answer the problem.
1.
2.
3.
1.
4.
5.
1.
2.
6.
Expressed as an If . . . Then statement
Experiment – Test of your hypothesis
Data – Information you collect during an experiment
Qualitative – describe using words
Quantitative – describe using numbers
Conclusion – State whether the data supports or refutes the
hypothesis
(Our Pizza Has Extra Delicious Cheese)
3. Define: experimental variable, controlled variable, control group,
experimental groups.
1.
Experimental variable – The variable that is measured
by the scientist; a.k.a the dependent variable
2.
Controlled variable – Constants. Things that are the
same for both the control and experimental groups.
3.
Control group – Does NOT receive the variable; used as
a comparison
4.
Experimental group – Receives the variable
4. Describe the difference between bar graphs and line graphs.
Explain a situation in which you’d use each.
1.
Bar Graph – When you want to compare several
things.
1.
Line Graph – Change over time.
5. What are the 6 rules you must follow when making good graphs?
1.
2.
3.
4.
5.
6.
Independent variable on the x–axis
Dependent variable on the y–axis
Label axes
Include units
Title graph
Use a ruler
6. Read the following experiment & answer the questions
(if an answer doesn’t exist, make improvements).
Stewie wanted to see which detergent would make his
favorite teddy bear (Rupert) the cleanest. He believed
that “Nature’s Best”, an environmentally friendly product
would work better than “Clean & Bright” which was the
leading brand. First he stained the left arm of Rupert
with a mixture of dirt, grape juice and Crayola markers.
He then repeated the same procedure on Rupert’s right
arm. Stewie then measured out the same amount of
water and he proceeded to handwash the stains in a
small basin scrubbing for 8 minutes using 10mLs of
“Nature’s Best” on the left arm. The whole process was
repeated using 10mLs “Clean & Bright” on the right arm.
6. Read the following experiment & answer the questions
(if an answer doesn’t exist, make improvements).
• What was Stewie’s hypothesis?
• IF I use both Nature’s Best and Clean & Bright detergent to
clean dirt, grape juice, and Crayola marker stains from my
Teddy bear, THEN Nature’s Best will get my Teddy the
cleanest.
• What was the independent variable?
• Brand of detergent
• What was the dependent variable?
• How clean Teddy’s arm was
6. Read the following experiment & answer the questions
(if an answer doesn’t exist, make improvements).
• What were the constants (controlled variables) in this experiment
•
Same type of stain, amount of detergent, scrubbing time
• What was the control group?
•
Staining a portion of teddy and not scrubbing it clean.
• If Stewie was to graph the data, what would appear on the X axis
•
Brand of detergent
• Y axis?
•
% of stain removed
• What kind of graph is this?
•
Bar graph
7.
A scientist studied the effects of various water pH levels on the heartrate
(heartbeats per minute) of a small crustacean called a Daphnia. He did
this by putting Daphnia in solutions varying in pH solutions and
counted the number of times their hearts beat in one minute.
• a. What would be the independent variable?
•
pH
• b. What would be the dependent variable?
•
Daphnia’s heartrate
7.
• Sketch a set up of the graph that could be made from his
data. Be sure that your graph follows all the rules of
“good graphs”
• d. Would it be a line graph or a bar graph? Why?
•
It shows the effect of the independent variable on the dependent
variable.
8. Explain the pH scale and numbering system used.
Which numbers are considered acids? Bases? Neutral?
• Acids – 0 6.9
• Neutral – 7.0
• Bases – 7.1  14
9. List the 4 major biological compounds, their building blocks,
their major functions, and 3 examples of each.
Compound
Building Block
Function
Example
Carbohydrate
Monosaccharide
Key source of
energy
Structure in plants
Lipid
Glycerol & 3 fatty
acids
Concentrated
source of energy
Saturated and
unsaturated
Protein
20 Amino acids
Structural
Speed up chemical
reactions
Keratin
enzymes
Nucleic Acid
Nucleotide
Stores genetic
information
DNA & RNA
Glucose
Starch
10. What is an organic compound? What elements do all organic
compounds contain?
• All contain carbon atoms that are covalently bonded to others
elements– typically hydrogen, oxygen, and other carbon atoms.
• Made from thousands or even hundreds of thousands of smaller
molecules.
• Examples:
•
•
•
•
Carbohydrates
Lipids
Proteins
Nucleic Acids
11. Explain the difference between monosaccharides, disaccharides, and
polysaccharides. Give an example of each.
• Monosaccharide – “Single sugar” Ex) glucose
• Disaccharide – “Double sugar”
Ex) sucrose; table sugar (glucose + fructose = sucrose)
• Polysaccharide – “Many sugars” Ex) starch
12. What is an enzyme? Give 3 examples of enzymes and state their
functions. Why are they an important part of our digestion?
• Enzymes are protein molecules. They speed up chemical reactions that
would otherwise take a long time. This is called catalyzing the reaction.
1.
Lactase breaks down lactose
2.
Catalase breaks down Hydrogen Peroxide
3.
Amylase breaks down starch
13. What is a substrate?
 The substance that an enzyme break down.
14. Using the diagram below, explain the lock-and-key theory in the space
below each graphic
14. Using the diagram below, explain the lock-and-key theory in the space
below each graphic
• The shape of the enzyme perfectly fits the shape of its substrate
•
Like a lock and a key!
• Therefore, enzymes will only work on one substrate
15. What does it mean for an enzyme to become “denatured?”
How might this happen?
• It changes shape and can no longer bind to its
substrate. Therefore, it can’t break it down.
• A change in temperature or pH.
16. What factors affect enzyme action?
How does each affect enzyme action?
• Temperature
• pH
• Enzymes operate most efficiently within a certain
temperature and pH range.
Unit 2
CELLS AND ENERGY
17. Examine the graphic below, is it a plant or animal cell?
• Animal Cell
• No cell wall
• No chloroplasts
• No central vacuole
18. Label the organelles below and identify the function of each.
A.
Ribosome – site of protein synthesis
B.
Mitochondria – Produces ATP
A.
Nucleus – Contains the DNA
A.
Centriole – Produces spindle fibers.
(formed from microtubles)
B.
Cell membrane – Regulates what
enters/exits the cell.
19. Explain several differences between plant and animal cells.
Explain several similarities.
Plant Cell
Rigid shape
Cell wall and
cell membrane
Chloroplasts
Central Vacuole
Animal Cell
Flexible shape
Just a cell
membrane
No chloroplasts
Smaller vacuole
20. Explain diffusion, osmosis, active transport, and passive transport.
List some similarities and differences.
• Passive Transport – Requires no energy from the cell. Takes advantage
of the natural movement of particles (follows the concentration
gradient).
•
Diffusion – Movement of molecules from an area of high
concentration to an area of low concentration until equilibrium is
reached.
•
Osmosis – Diffusion of water.
• Active Transport – Requires energy from the cell. Moves material
against the concentration gradient (from low to high).
Passive Transport
Active Transport
21. Create sketches to explain what happens to a cell when it is in a
hypotonic solution, a hypertonic solution, and an isotonic solution.
22. Determine total magnification by completing the table below:
 Total Magnification = Objective Lens x Eye Piece
23. Which one will have the most organisms in the field of view?
Which one has the least?
• Most – 80x Magnification. It is not zoomed in as
much, so the field of view is much larger
• Least – 200x Magnification. It is zoomed in much
more, so it has a smaller field of view. You will see
fewer organisms, but in greater detail.
24. Label the parts of a microscope and give their functions.
Eyepiece
Body tube
Revolving
nosepiece
Objective lens
Coarse focus
Stage
Fine focus
Diaphragm
Light source
Power switch
25. What is the difference between prokaryotic and eukaryotic cells?
Give an example of each.
• Prokaryotic – Does not
contain a nucleus
•
Ex) Bacterium
• Eukaryotic – Contains a
nucleus and membrane
bound organelles
•
Plant or animal cell
26. Write the general equation of photosynthesis.
• 6CO2 + 6H2O  C6H12O6 + 6O2
• Carbon dioxide + Water  Glucose + Oxygen
27. What is the purpose of photosynthesis?
 Plants convert the light energy from sunlight into
chemical energy in the form of Glucose (sugar)
 In this process, they release the oxygen we need to
breathe.
28. What effect do increases in temperature, CO2 or light have on the rate
of photosynthesis?
• Temperature – Rate of photosynthesis will increase
and then decrease.
• CO2 and Light Intensity – Rate of photosynthesis will
increase and then level off.
29. Write out the equation for cellular respiration.
• 6O2 + C6H12O6  6H2O +6CO2 + 36 ATP
• Oxygen + Glucose  Carbon dioxide + Water + ATP
30. What is the purpose of cellular respiration?
• The process by which cells produce energy (ATP)
from carbohydrates.
31. Where do respiration and photosynthesis occur in a cell?
 Respiration – Mitochondria in animal AND PLANT
CELLS
 Photosynthesis – Chloroplasts in plant cells
32.Why is ATP so important to living things?

ATP provides cells the energy they need to
carry out ALL activities
 Cell division
 Growth
 Repair
 And many, many more . . . Everything!
33. Compare and contrast respiration and photosynthesis.
Respiration
Occurs in plants
AND animals
Takes place in the
mitochondria
O2 + C6H12O6 are
reactants
H2O +CO2 + ATP are
products
Photosynthesis
Occurs only in plants
Takes place in the
chloroplasts
H2O +CO2 + light are
reactants
O2 + C6H12O6 are
products
Unit 3
EVOLUTION AND CLASSIFICATION
34. Explain the parts of Darwin's theory of Evolution by natural selection.
1)
The members of a population have heritable variations.
• size, coloration, strength, behavior
2)
In each population, many more individuals are produced each
generation than the environment can support.
3)
Some individuals possess adaptations that enable them to survive
and reproduce more than other individuals.
4)
An increasing number of individuals in succeeding generations
possess the adaptation.
5)
The result of natural selection is a population adapted to its local
environment.
34. Explain the parts of Darwin's theory of Evolution by natural selection.
Natural Selection Stated Simply . . .
1)
2)
3)
4)
5)
Variation within a population
Struggle for existence
Survival of the fittest
Descent with modification
Change over time
35. Explain in detail how Darwin would explain the evolution of giraffes
from a population of ancestors that had short necks.
• Within a population of giraffes, some have a longer neck than others
•
•
•
•
(variation).
Giraffes are always competing for food (struggle for existence).
Those giraffes with a longer neck will be able to reach more food
(survival of the fittest).
They will survive to reproduce and pass the beneficial trait on to their
offspring (descent with modification).
Over time, the population of giraffes will have more members with
longer necks (change over time).
36. Explain Lamarck's theory of evolution.
Include use/disuse and acquired characteristics.
• The more an organism uses a structure, the more developed it will
become. For example, a giraffe will continually stretch its neck to reach
the leaves in the upper canopy of the trees. Over its lifetime, the giraffe
will ACQUIRE a longer neck. The giraffe can pass this acquired trait
onto its offspring. We now know this is not correct! ACQUIRED
TRAITS ARE NOT INHERITED!
37. Describe 5 evidences that support evolution.
1.
2.
3.
4.
5.
fossils – Paleontologists can compare fossils from the past to
organisms living today.
homologous structures – Organisms have very similar structures that
have been modified for different functions.
vestigial structures – A remnant (left over) structure that no longer
serves a purpose but was useful in an ancestral stage.
embryology – Organisms that are very different (i.e. a fish and a
human) still have very similar stages of embryonic (pre–birth) stages
of development.
DNA – The more recently two species share a common ancestor, the
more similar their DNA will be. Organisms that do not share a recent
common ancestor, will have a greater % difference in their DNA
38. Explain the 3 types of selection (directional, disruptive, and
stabilizing).
• Stabilizing – The norm is selected for and the
extremes are selected against.
• Directional – One extreme is selected for.
• Disruptive – The norm is selected against and the
extremes are selected for
39. What is Binomial Nomenclature? What are the rules for writing a
scientific name? Give an example.
• Two word naming system
• Genus name is first, capitalized
• Species name is second, not capitalized
• Entire name is either underlined OR italicized
• Ex) Homo sapiens
40. Who created the modern system for classification?
• Carolus Linnaeus is
considered the “Father
of Taxonomy”
41. List the taxonomic categories in order from most general to specific.
Which organisms are most closely related? Which are least closely
related?
• Domain  Kingdom  Phylum  Class  Order  Family  Genus
 Species
• Does King Phillip chew on fat green stems?
• As you move toward the species taxon, organisms are more closely
related.
• Ex) In the Animal Kingdom you have organisms that are very different;
sponge and Chimpanzee
• In the Class Mammalia, organisms are more similar to one another
since they are all mammals.
42. List the characteristics of each of the 6 kingdoms and give an example
of two organisms in each kingdom.
43. What determines whether 2 organisms are members of the same
species?
 Only members of the same species can breed and
produce FERTILE offspring.
44. How are fossils used by scientists to support the theory of natural
selection?
• Fossil – The trace (ex: footprints) or remains of an
organism that lived long ago, preserved in
Sedimentary rock.
• Paleontologists can examine the fossil record and
observe how species have changed over time.
Unit 4
GENETICS I – DNA, RNA,
AND PROTEIN SYNTHESIS
45. Who were Hershey and Chase?
Explain their experiment and what it proved.
• Worked with bacteriophages (viruses), which are made of only DNA
and protein
• Alternated between using radioactive DNA or radioactive protein
•
•
Sulfur isotope (35S) – only found in protein coat
Phosphorous isotope (32P) – only found in DNA
• Looked to see if bacteria became radioactive when radioactive DNA or
when radioactive protein was inserted by the virus
• The bacteria only became radioactive when radioactive DNA was used
• Conclusion – DNA is what is inserted into the bacteria, not the protein!
• Hershey Chase Video Clip
The Hershey and Chase Experiment
46. Who was Griffith? Explain his experiments and what he proved.
• Examined Streptococcus pneumoniae strains and mice
• S strain of bacteria cause pneumonia
• R strain of bacteria does NOT cause pneumonia
• S strain of bacteria can be killed and rendered harmless by heating
• R bacteria mixed with heat-killed S bacteria can still cause infection
• Conclusion – Some type of material can move from the heat–killed S
bacteria to the R bacteria to cause disease, and that this must be the
genetic material—TRANSFORMATION
• Transformation – change in the genotype (genetic makeup of an
organism) caused when cells take up foreign genetic material
• The cause of transformation was not known at the time
• Griffith's Experiment Video Clip
Griffith’s Experiment – 1928
47. Who are Watson and Crick? What did they do for the field of biology?
• The structure of DNA
was discovered in 1953
by James Watson and
Francis Crick.
• They received the Nobel
prize.
48. Draw a diagram of a DNA molecule containing 4 base pairs. Label the
following: deoxyribose, phosphate, adenine, guanine, cytosine, thymine,
nucleotide, hydrogen bonds covalent bonds.
Covalent bonds
49. What is a nucleotide?
What is a nucleotide made up of (be specific)?
• Nucleotide – Building bock of a nucleic acid (DNA or
RNA)
• Made up of a sugar, phosphate, and nitrogen base
50. What is DNA replication? Explain the process of DNA replication?
What enzymes are involved in this process?
• DNA Replication – When DNA makes a copy of itself.
• The two strands of DNA are separated by enzymes called helicases that
break hydrogen bonds as they move along the strand.
• Enzymes called DNA polymerases bind to the chains and assemble new
strands of DNA by attaching a new nucleotide to the complementary
strand.
• The end result is two pieces of DNA that are each half new and half old
DNA.
• Errors are repaired by other enzymes that “proofread” the new DNA.
DNA Replication
51. Why is replication of DNA important to organisms?
• The cell must replicate (copy) the DNA in order to
have two sets for each new daughter cell after
mitosis.
52. What happens during transcription? Explain the process.
• Transcription – Process of copying DNA into RNA.
This is the first phase of protein synthesis which
takes place in the nucleus.
53. What occurs during translation?
Explain the process.
 Translation – The second part of protein synthesis takes place at the
ribosome. The mRNA that was made in transcription travels out of the
nucleus and to a ribosome on the ER or in the cytoplasm.
 Amino acids that are freely floating in the cytoplasm are transported to
the ribosome by the tRNAs. Part of the tRNA contains a region of three
bases called the anticodon. Only the anticodon that matches the mRNA
codon will be able to donate an amino acid so that the DNA’s message
is translated into a protein correctly.
Translation
54. How many bases are needed to code for 1 amino acid?
What is this called on mRNA?
• 3 bases code for 1 amino acid
• Called a codon
55. What are 3 differences between RNA and DNA?
RNA
 Contains the nitrogen
base Uracil
DNA
 Contains the nitrogen
base Thymine
 Sugar is Ribose
 Sugar is Deoxyribose
 Single stand
 Double strand
 Can leave nucleus
 Can’t leave nucleus
56. What are 3 differences between mRNA, rRNA and tRNA?
• Messenger RNA (mRNA) – Made by copying the
DNA, takes the message to the ribosome to make
proteins allowing the DNA to safely stay in the
nucleus.
• Transfer RNA (tRNA) – Carries the correct amino
acid to the ribosome from the cytoplasm to add it
to the protein, very specific.
• Ribosomal RNA (rRNA) – Makes up the ribosome.
57. Transcribe this DNA to mRNA, then to tRNA,
then determine its amino acid sequence:
• DNA  T A C | G C T | A C C | A T C | A G T
• mRNA  A U G | C G A | U G G | U A G | U C A
• tRNA  U A C | G C U | A C C | A U C | A G U
• Amino acid sequence  start, arginine,
tryptophan, stop, (serine)
58. What are the three types of point mutations? Which ones will cause
the most harm? Which might have no effect at all?
• Addition – One or more bases are added to the
•
•
•
•
strand.
Deletion – One or more bases are omitted from the
strand.
Substitution – One base is put in the strand in
place of another
Most harm – Addition & deletions since they will
cause a frameshift.
No effect – When the same amino acid is inserted.
•
UCU, UCC, UCA, and UCG all code for serine
Types of Mutations
59. What is cancer? What are some causes of cancer? Treatments of
cancer? Ways to prevent cancer?
• Cancer – Cells divide at an uncontrolled rate. Essentially, it is a
disorder of cell division.
• Oncogenes become more active speeding up cell division
• Tumor suppressor genes (prevent cell division from occurring too
often) are damaged
• Causes – Environmental factors (pollution, pesticides, radiation)
• Treatments – Anticancer drugs, chemotherapy, radiation, surgery.
• Prevention – Don’t smoke, proper diet, exercise, have regular medical
exams for early detection.
60. What is a mutagen? Carcinogen?
• Mutagen – Cause damage to DNA leading to
mutation. Ex) radiation
• Carcinogen – Anything that causes cancer.
61. What types of cells are diploid? What types of cells are haploid ?
• Diploid – Somatic cells (body cells)
• Haploid – Gametes (sperm and eggs)
62. What is a somatic cell?
• Somatic cells – ANY body cells that are NOT sperm
or egg
63. Answer the following questions and assume you are using a human
cell with 46 chromosomes:
a) What is the diploid number? 46
a) What is the haploid number? 23
b) If this cell went through mitosis, how many
chromosomes would the daughter cells have? 46
c) If a cell went through meiosis how many
chromosomes would the daughter cells have? 23
64. What is genetics?
•
Genetics – The science of heredity and of the
mechanisms by which traits are passed from
parent to offspring.
65. Diagram out a cell going through mitosis as well as a cell going
through meiosis. Assume you start with a cell with 6 chromosomes.
Be sure to note what is going on and any similarities/differences.
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
Mitosis vs. Meiosis
MEIOSIS
MITOSIS
• A type of cell division
• A type of cell division
• Produces somatic cells (body)
• Produces gametes (sperm &
ova)
• Results in two daughter cells
• Results in four daughter cells
•
Daughter cells are genetically
identical to parent cell
• Daughter cells are genetically
different to parent cell
• Daughter cells are diploid
• Daughter cells are haploid
66. What are the major functions of mitosis?
What are the major functions of meiosis?
• Mitosis – A type of cell division that produces somatic cells.
• Meiosis – A type of cell division that results in gametes.
•
•
Only occurs in gonads (sex organs)
• Male – testes
• Female – ovaries
Produces haploid cells
• Haploid – half set of chromosomes
• Diploid – full set of chromosomes
• The process of meiosis maintains the chromosome number.
Egg + sperm = zygote
23 + 23 = 46
67. Who was Gregor Mendel?
What did he do?
• Gregor Mendel was an Austrian
monk who studied the
inheritance patterns in pea
plants. His knowledge of
statistics allowed him to make
very accurate studies of seven
traits in peas and how they were
passed from one generation to
the next.
• He began the study of genetics
and is considered the Father of
Genetics.
68. What are alleles?
• Alleles – Form of a trait, Aa
• Can either be dominant or recessive
69. Concept generalization:
• Dominant – Expressed
• Recessive – Masked by dominant allele
• Homozygous – Two of the same alleles, AA or aa
• Heterozygous – Two different alleles, Aa
• Genotype – What alleles a person has, AA, Aa, or aa
• Phenotype – Physical appearance based on genotype, brown eyes
• Allele – Form of a trait, dominant (A) or recessive (a)
• Test cross – See question # 71
• Genotypic ratio – Predicted genotypes in F1 generation
• Phenotypic ratio – Predicted phenotypes in F1 generation
70. List and explain Mendel’s three laws.
• Law of Dominance – When two different alleles occur together (in a
heterozygous individual; Aa) one of them may be completely expressed,
while the other may have no observable effect on the organism’s
appearance.
• Law of Segregation – Two alleles for a trait segregate (separate) during
meiosis when gametes are formed.
• Law of Independent Assortment – The inheritance of one trait does
NOT influence the inheritance of another trait.
71. What is a test cross?
Why is it used?
• Test cross – Used to determine the genotype of an individual with a
dominant phenotype in order to determine if they are Heterozygous or
Homozygous dominant. You will cross them with a homozygous
recessive individual. If offspring are produced with the recessive
phenotype, the individual must be Heterozygous.
72. Two pink 4 o’clock flowers are crossed.
What will be the genotypes and phenotypes of their offspring?
R
r
R
RR
Rr
r
Rr
rr
• What is the genotypic ratio?
1RR : 2Rr : 1rr
• What is the phenotypic ratio?
• 1 Red : 2 pink : 1 white
•
73. A man with colorblindness marries a woman whose mom was
colorblind and dad was normal.
Xb
Y
XB
XBXb
XBY
Xb
XbXb
XbY
• What are the chances that their kids will be
colorblind?
• 50 %
74. Solve these multiple allele problems.
Show genotypes and phenotypes of the offspring.
A. Blood types AB x OO
A
B
O
AO
BO
O
AO
BO
74. Solve these multiple allele problems.
Show genotypes and phenotypes of the offspring.
B. Could a man with A blood and a woman with B
blood have a child with O blood? YES!
A
O
B
AB
BO
O
AO
OO
75. Flower color is incompletely dominant in four-o-clocks. How
could offspring that are only pink be obtained? Be sure to show all work!
• Cross a red flower (RR) with a white one (rr). ALL
the offspring will be pink (Rr)
R
R
r
Rr
Rr
r
Rr
Rr
76. What is the difference between autosomes and sex chromosomes?
Autosomes – Not involved in determining the sex of
an individual. Chromosomes 1 – 22
Sex Chromosomes – 23 pair. Contain genes that will
determine the sex of the individual.
77. What determines the sex of a human?
• The Sex Chromosomes they inherit.
• Females – XX
• Males – XY
78. A color-blind man whose mother was homozygous for dark skin and
father was light skinned marries a woman whose father was color blind
and light skinned and mother was also light skinned.
• What are the possible genotypes and phenotypes for their offspring?
Assume that dark skin is dominant to light skin.
• This is a dihybrid Cross with one of the traits being sex–Linked!
• First draw a pedigree to figure out the genotypes of the individuals.
dd BX
dd bY
dd Bb
DD Bb
dd BY
Dd bY
78. A color-blind man whose mother was homozygous for dark skin and
father was light skinned marries a woman whose father was color blind
and light skinned and mother was also light skinned.
• What are the possible genotypes and phenotypes for their offspring?
Assume that dark skin is dominant to light skin.
• This is a dihybrid Cross with one of the traits being sex–Linked!
• Then FOIL to figure out possible allele combinations in parent gametes
dXB
dXb
DXb
DdXBXb
DdXbXb
DY
DdXBY
DdXbY
dXb
ddXBXb
ddXbXb
dY
ddXBY
ddXbY
# 79
• A man who is heterozygous for being tall and has attached earlobes
marries a woman who is short and heterozygous for unattached
earlobes. List out the gametes for both parents and the genotypic and
phenotypic ratios.
• Key
• T= tall
• t = short
• E = Unattached earlobes
• e = attached earlobes
•
•
Man = Ttee
Woman = ttEe
# 79 Continued
• A man who is heterozygous for being tall and has attached earlobes
marries a woman who is short and heterozygous for unattached
earlobes. List out the gametes for both parents and the genotypic and
phenotypic ratios.
• FOIL to find the combination of alleles that can occur in the gametes
•
Man = Ttee = Te, Te, te, te, or Te and te
•
Woman = ttEe = tE, te, tE, te, or tE and te
•
Now, do the cross . . .
# 79 Continued
• A man who is heterozygous for being tall and has attached earlobes
marries a woman who is short and heterozygous for unattached
earlobes. List out the gametes for both parents and the genotypic and
phenotypic ratios.
Te
te
• T= tall
TtEe
ttEe
tE
• T = short
• E = Unattached earlobes
• e = attached earlobes
te
•
•
Ttee
ttee
Genotypic ration – 1 TtEe : 1 ttEe : 1Ttee : 1ttee
Phenotypic ratio – 1 Tall w/ unattached : 1 short w/ unattached : tall
w/attached : 1 short w/ attached
80. What is nondisjunction? When does it occur?
Provide 3 examples of nondisjunction disorders.
 Nondisjunction – When the chromosomes do not separate properly
during meiosis.
 A gamete (sperm, egg) ends up with an extra or missing chromosomes
as a result
 Ex) Downs Syndrome – Trisomy 21
 Klinefelter’s Syndrome – XXY or XXXY. Males receive an extra X
chromosome.
 Turners Syndrome – X0; Sterile female who is missing or has an
incomplete X chromosome
81. What is a karyotype?
How is it used by biologists?
 Picture of a person’s chromosomes
 To see if the have a monosomy (missing a chromosome) or a trisomy
(extra copy of a chromosome)
81. Draw a Pedigree for the following family.
 A straight thumb is recessive to a curved (hitchiker's) thumb. Bob and
Linda are a married couple. Bob has a hitchhikers thumb like his
father, but his mother did not. Linda has a straight thumb as do both of
her parents. Bob and Linda have three children: A boy with hitchikers
thumb, a boy with a straight thumb, and a girl with a straight thumb.
T_
T_
tt
Linda, Tt
tt
T_
Bob, Tt
T_
tt