Question 1

Which of the following best describes the inheritance pattern of the A\^Y allele in mice?

Accepted Answer

A\^Y is dominant for coat color but recessive for lethality.

Question 2

If two A\^Y A mice are crossed, what is the expected phenotypic ratio among the surviving offspring?

Accepted Answer

2 yellow : 1 agouti

Question 3

Why do A\^Y A\^Y mice die before birth?

Accepted Answer

Because the A\^Y allele deletes the regulatory region of the agouti gene and part of the adjacent Merc gene, causing lethality when both copies are affected.

Question 4

Which genotype results in a solid black coat color in mice?

Accepted Answer

aa

Question 5

A cross between an A\^Y a mouse and an Aa mouse produces which phenotypic ratio for coat color?

Accepted Answer

1 yellow : 1 agouti : 1 white

Question 6

What is epistasis?

Accepted Answer

When the expression of one gene masks or modifies the expression of another gene.

Question 7

In mouse coat color genetics, which locus is epistatic to the Agouti locus?

Accepted Answer

B locus

Question 8

What is the expected F2 phenotypic ratio for coat color in a cross between two AaBb mice (where B is required for any color and bb is albino)?

Accepted Answer

$$9:3:4$$

Question 9

Which F2 genotype from a cross of AaBb x AaBb will result in an albino mouse?

Accepted Answer

aabb

Question 10

If a mouse is bb at the B locus, what will its coat color be regardless of its genotype at the Agouti locus?

Accepted Answer

Albino

Question 11

A cross between an A\^Y a Bb mouse and an Aabb mouse is performed. Using the product law, what is the expected ratio of colored to albino offspring?

Accepted Answer

$$3:1$$

Question 12

Which of the following statements about genetic linkage is correct?

Accepted Answer

Linked genes are located close together on the same chromosome and are more likely to be inherited together.

Question 13

If two genes are 1 centiMorgan (cM) apart, what is the probability that their alleles will NOT be inherited together?

Accepted Answer

$$1\%$$

Question 14

Which of the following best explains why the expected ratio from a cross of two A\^Y A mice is not 3:1?

Accepted Answer

Because A\^Y A\^Y genotype is lethal and those offspring do not survive.

Question 15

Which of the following is a real-world example of epistasis?

Accepted Answer

The Bombay phenotype in human ABO blood groups.

Question 16

A mouse with genotype AaBb is crossed with a mouse of genotype AaBb. What fraction of the F2 generation will be albino?

Accepted Answer

$$3/16$$

Question 17

Which of the following is true regarding recombination frequency between two linked genes?

Accepted Answer

It decreases as the distance between the genes decreases.

Question 18

If two genes are not linked, what is the probability that their alleles will be inherited together?

Accepted Answer

$$50\%$$

Question 19

Which of the following best describes the function of the B locus in mouse coat color genetics?

Accepted Answer

It is required for any color to be present; bb homozygotes are albino.

Question 20

A researcher observes that two genes are inherited together 99% of the time. What is the most likely distance between these genes?

Accepted Answer

$$1\ \mathrm{cM}$$

Genetics Study Notes: Mouse Coat Color, Epistasis, and Genetic Linkage

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