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 a. Deduce the genotype of each albino mice, to the extent that is possible, in the following table. Explain your answers. b. Deduce the genotype and phenotype of each parent in the following table. Explain your answers. c. A gray-colored rat is mated with one that is yellow. The offspring include an albino rat and a cream-colored rat. Diagram this cross. Be sure to include the square and the phenotypic ratio in the offspring.

Explanation / Answer

Albino 1 will have the genotype AABBcc and albino 2 will have the genotype AAbbcc.

The reason behind these genotypes is that for a rat to be albino it should have both the recessive alleles of gene C. For all gray offsprings in the F1 generation the presence of dominant alleles of A and B are needed and will give 3/4 and 1/4 ratio in the F2 generation. For albino 2 we know that yellow rats appear in the F2 generation which means that there should be presence of recessive allele of gene B in the parent alongwith dominant A and recessive c.

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