Pigment in mouse fur is only produced when the C allele is present. Individuals of the cc genotype are white. If color is present, it may be determined by the A, a alleles. AA or Aa results in agouti color, while aa results in black coats. What are the phenotypic ratios in the F2 generation of mice if an AACC parent and an aacc parent are bred to yield F1 mice which are then crossed to generate an F2 generation? Enter your answer as a fraction in the blank next to the appropriate coat color.

agouti __

colorless_

black______

The type of genetic pattern that is followed in this cross is epistasis, in this pattern the phenotypic expression of a particular gene in one locus changes the effect of the gene on other locus.

In this case allele C present will leads to the color but homozygous C denotes colorless and A denotes agouti where aa denotes black. With the first cross all F1 individual will be AaCc . Hence, in the second cross for F2 would be AaCc × AaCc

Thus, the phenotypic ratio of all three type of coat color woyld be agouti: colourless:black=9:4:3 so the agouti coat color would be 9/16 , Colourless coat color would be 1/4 , and Black would be 3/16 .