26. A dominant gene, A, causes yellow color in rats. The dominant allele of another independent gene, R, produces black coat color. When the two dominant genes occur together (A-R-), they interact to produce grey coat color. Rats of the double recessive genotype are cream-colored. If a grey male and a yellow female are mated and produce approximately 3/8 yellow, 3/8 grey, 1/8 cream, and 1/8 black, what were the genotypes of the parents?

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Arclight Arclight · Answer 1 · 2020-05-16T06:06:37+02:00

Answer:

male = AaRr; female = Aarr

Explanation:

Let the dominant allele for black coat color be "R" and its recessive allele be "r"

Like wise let the dominant allele for yellow color in rats be "A" and its recessive allele be "a"

It is given that double recessive genotype are cream-colored i.e aarr would be cream colored.

Gametes of male AaRr - AR, aR, Ar, ar

Gametes of female Aarr - Ar, Ar, ar, ar

AR aR Ar ar

Ar AARr AaRr AArr Aarr

ar AaRr aaRr Aarr aarr

Yellow offspring – Aarr (4), AArr (2), total 6 out of 16, hence probability is 3/8

Grey offspring – AARr (2), AaRr (4) total 6 out of 16, hence probability is 3/8

Cream offspring – aarr (2), total 2 out of 16, hence probability is 1/8

Black offspring – aaRr (2), total 2 out of 16, hence probability is 1/8