In rats, several independently assorting autosomal genes affect coat color. Gene

Question

In rats, several independently assorting autosomal genes affect coat color. Gene A controls the distribution of yellow pigment in hair, and gene B causes black pigmentation. The two genes interact as follows: A–B– (gray), A–bb (yellow), aaB– (black), and aabb (cream). These genotypes are only expressed in the presence of the dominant allele of a third gene, C; rats with genotype cc are albino.

a.    Deduce the genotype of each albino mice, to the extent that is possible, in the following table. Explain your answers.

True-breeding parents

F1

F2 offspring

Gray x albino-1

All gray

3/4 gray : 1/4 albino

Gray x albino-2

All gray

9/16 gray : 3/16 yellow : 4/16 albino

True-breeding parents

F1

F2 offspring

Gray x albino-1

All gray

3/4 gray : 1/4 albino

Gray x albino-2

All gray

9/16 gray : 3/16 yellow : 4/16 albino

Explanation / Answer

Gray parents are AABBCC and albino-1 parents are AABBcc. gamate will be ABC and ABc. F1 generation will be AABBCc which is all gray.

Gray parents are AABBCC and albino-2 parents are AAbbcc. gamete will be ABC and Abc. F1 generation will be AABbCc whch is all gray.

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