Question

Consider a gene that affects fur color in mice. this gene has two alleles, a and a. if aa mice have white fur, aa mice have gray fur, and aa mice have black fur, how would we describe the effect of these alleles?

a. a is dominant and a is recessive.
b. a is recessive and a is dominant.
c. a and a are codominant.
d. a and a are epistatic.

Answer 1

The alleles determining fur color in mice, where 'a' results in white fur and 'a' in gray or black fur, illustrate a form of dominance, but the interaction with a separate gene responsible for pigment production (C) is an example of epistasis, where 'c' is epistatic to the 'a' gene. The answer is option D a and a are epistatic.

Step-by-step explanation:

The effect of the alleles on fur color in mice, where aa individuals have white fur, aa individuals have gray fur, and aa individuals have black fur, suggests a form of dominance. However, considering additional information on mouse pigment genetics, we learn that a separate gene locus (C) is responsible for pigment production.

When the gene at this locus is homozygous recessive (cc), it results in an albino mouse, regardless of the genotype at the fur color locus (aa or aa). This is an example of epistasis, where one gene masks or modifies the expression of another gene. Specifically, the C gene is epistatic to the aa gene. Thus the correct answer to the student's question would be a and a are epistatic.