Download wiki review on classical genetic

Review Guide:
Classical Genetics
Name: ____________________________________________
Date: _________________
Instructions: This is a review guide of the topics covered in our unit on classical genetics. Use this as a method of
studying for your Unit . This review guide, if completed, can be submitted for extra credit on your exam.
Part I: Vocabulary
The following is a list of terms you will be expected to know for your exam. For each term, record the correct definition
from your notes.
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Genetics
Gene
DNA
Genotype
Phenotype
Homozygous
Heterozygous
Dominant
Recessive
Punnett Square
Dihybrid Cross
Sex-Linked Trait
Codominance
Incomplete Dominance
Trait
Allele
Autosome
Purebred
Hybrid
Part II: Practice Selected Response
For each of the following multiple choice questions, choose the most correct answer AND make sure to show your work
in order to receive full credit.
1. In pea plants, spherical seeds (S) are dominant to dented seeds (s). In a genetic cross of two plants that are
heterozygous for the seed shape trait, what fraction of the offspring should have spherical seeds?
1. None
2. 1/4
3. 1/2
4. 3/4
2. A genetic cross between two hybrid pea plants having yellow seeds will yield what percent green-seeded plants?
Yellow seeds are dominant to green.
1. 0 %
2. 25 %
3. 50 %
4. 75 %
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Review Guide:
Classical Genetics
3. In Mendel’s experiments, if the gene for tall (T) plants was incompletely dominant over the gene for short (t) plants,
what would be the result of crossing two Tt plants?
1. 1/4 would be tall; 1/2 intermediate height; 1/4 short
2. 1/2 would be tall; 1/4 intermediate height; 1/4 short
3. 1/4 would be tall; 1/4 intermediate height; 1/2 short
4. All the offspring would be tall.
4. In a cross between a white-eyed female fruit fly and red-eyed male, what percent of the female offspring will have
white eyes? (Eye color in fruit flies is sex-linked, with red eyes the dominant trait)
1. 100 %
2. 25 %
3. 50 %
4. 75 %
5. Hemophilia in humans is due to a sex-linked mutation. What will be the results of mating between a normal (noncarrier) female and a hemophiliac male?
1. half of daughters are normal and half of sons are hemophiliac
2. all sons are normal and all daughters are carriers
3. half of sons are normal and half are hemophiliac; all daughters are carrers
4. all daughters are normal and all sons are carriers
6. A human female “carrier” who is heterozygous for the recessive, sex-linked trait red green colorblindness marries a
normal male.
What proportion of their female offspring will show the trait?
1. all
2. 1/2
3. 1/4
4. 0
Part III: Practice Free Response
For each of the following free response questions, show your work AND explain your answer to receive full credit. Be
prepared for this type of question to appear on your Exam.
1. If a homozygous black sheep (BB) is crossed with a homozygous white sheep (bb), what is the probability that the
offspring will have black wool? Show your Punnett Square and write a sentence answer. Give all genotype and
phenotype %’s.
2. Set up a Punnett Square using the following information.
• Dominant allele for tall plants = D
• Recessive allele for dwarf plants = d
• Dominant allele for purple flowers = W
• Recessive allele for white flowers = 2
• Cross two heterozygous parents (DdWw)
3. The size of a pig’s snout is an inherited trait. The allele for short snouts is dominant (N) over the allele for long snouts
(n). A farmer mates two short-snouted pigs (parents). One parent is homozygous and the other is heterozygous for this
trait. A litter of twelve piglets, all with short tails, is produced (first generation). The farmer mates one of the first
generation pigs with a short-snouted pig from another litter. A litter of ten piglets is produced (second generation).
The breeder is surprised when one of the second generation piglets has a long snout.
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Review Guide:
Classical Genetics
Describe the genetic make-up of the parents and piglets that produced this inheritance pattern.
In your response, be sure to:
• Identify the genotype of the parents
• Use a Punnett Square to show the possible genotypes of the first generation piglets
• Use a Punnett Square to show the possible genotypes of the second generation piglets
• Identify the genotypic and phenotypic ratios of the first and second generation piglets
• Explain how a long-snouted piglet can suddenly appear when all the other pigs were short-snouted
4. Analyze the pedigree below showing the inheritance of disease A. In answering the question, use the letter A when
asked to determine genotypes.
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Based on the pedigree above, what type of inheritance pattern do you believe disease A to have (autosomal
dominant, autosomal recessive, sex-linked)?
What do you believe the genotypes of people I-2 and II-3 to be? Why?
What do you believe the genotypes of people IV-1 and IV-3 to be? Why?
If individual IV-2 had children with a man heterozygous for disease A, what would be the percentage chance
of having a child with disease A?
5. Fur color in a breed of dogs is controlled by codominance. Show the results of a cross between a black and a white
dog. What percentage of the offspring are white? Black? Grey? Spotted? How do you know?
6. Seed color in peas is controlled by incomplete dominance. Show the results of a cross between a green and a yellow
seed. What percentage of the offspring are green? Yellow? Yellow-green? Spotted? How do you know?
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