Question

In laboratory mice, the normal gray color is dominant over the albino (all-white) color. Starting with a purebred albino and a purebred gray as parents, what is the ratio of phenotypes in the F2 generation?

Answer 1

The F2 generation phenotypic ratio when crossing mice that are heterozygous for both coat color and pigment production (AaCc) is 9 agouti:3 solid color:4 albino. This example demonstrates epistasis, where the presence of the cc genotype leads to an albino phenotype, regardless of the A gene's alleles for coat color.

Step-by-step explanation:

The question is asking about the phenotypic ratio in the F2 generation of mice when a purebred albino and a purebred gray mouse are used as parents. This is an example of Mendelian genetics and more specifically, a case of epistasis, where one gene's effect masks the expression of another gene. Using the information provided, we know that the C gene is necessary for pigment production and is epistatic to the A gene, which determines the coat color being gray or albino.

In this case, when crossing heterozygotes for both genes (AaCc x AaCc), the phenotypic ratio will be 9 agouti (mottled agouti coat color):3 solid color (gray or black):4 albino (all-white color), as the aa genotype would produce solid coloration, but the presence of the cc genotype in any combination (AAcc, Aacc, or aacc) results in albino coloration regardless of the A allele present.