Final Exam

Question 1

1. How many offspring genotypes are expected in a trihybrid cross between parents heterozygous for all three traits when the traits behave in a dominant and recessive pattern? How many phenotypes?

Answer 1

Number of genotypes: 27 & Number of phenotypes: 8

Question 2

2. If black and white true-breeding mice are mated and the result is all gray offspring, what inheritance pattern would this be indicative of?

Answer 2

This blending in the phenotype is characteristic of incomplete dominance.

Question 3

3. Imagine you are performing a cross involving seed color in garden pea plants. What F1 offspring would you expect if you cross true-breeding parents with green seeds and yellow seeds? Yellow seed color is dominant over green.

Answer 3

Genotype of F1: All Yy.
Phenotype of F1: All yellow seeds.

Question 4

2. Assuming no gene linkage, in a dihybrid cross of AABB x aabb with AaBb F1 heterozygotes, what is the ratio of the F1 gametes (AB, aB, Ab, ab) that will give rise to the F2 offspring?

Answer 4

The ratio of the F1 gametes (AB, aB, Ab, ab) that will give rise to the F2 offspring is 1:1:1:1.

Question 5

3. A labrador retriever’s fur color is controlled by two alleles, E and B. Any dog with the ee__ genotype develops into a yellow lab, while B_E_ dogs become black labs and bbE_ dogs become chocolate labs. This is an example of ____ .

Answer 5

recessive epistasis.

Question 6

4. A scientist pollinates a true-breeding pea plant with violet, terminal flowers with pollen from a true-breeding pea plant with white, axial flowers. Which of the following observations would most accurately describe the F2 generation?

Answer 6

The F2 generation will display four phenotypes in a 9:3:3:1 ratio, with combinations of flower color (violet or white) and flower position (axial or terminal).

Question 7

5. If the allele encoding polydactyly (six fingers) is dominant, why do most people have five fingers?

Answer 7

Most people have five fingers because the dominant allele for polydactyly is rare, and the allele for five fingers is more common in the human gene pool.

Question 8

6. In pea plants, purple flowers (P) are dominant to white flowers (p) and yellow peas (Y) are dominant to green peas (y). What genotype is not possible for a cross between PpYY and ppYy pea plants?

Answer 8

The genotype Ppyy (or any genotype with yy) is not possible in this cross

Question 9

7. When two genes are located in close proximity on the same chromosome, they are considered ________, and their alleles tend to be transmitted through meiosis together.

Answer 9

linked