Question.1. In Guinea pigs, black fur (\"A\") is dominant to the albino conditio

Question

Question.1. In Guinea pigs, black fur ("A") is dominant to the albino condition ("a"), which produces white fur. A female from a homozygous black strain carries ovaries transplanted from an albino female. The albino female has received in turn the ovaries from the homozygous black animal. a) What are the expected results when the black female is mated to a black male, which has a white parent? b) What results are to be expected if the albino female is mated to the same male? Diagram the cross. c) Suppose the black female used in the transplant study had a white parent. Would this change your answers to parts (a) and (b) above? Explain.

Explanation / Answer

The allele is passed through gametes, so the strain of the guineapig from which ovary is transplanted is important to find out the results of the crosses.

Homozygous black (AA)-------> albino female-------> Homozygous black (ovary transplant)

a) genotype of black male, which has a white parent- Aa

Aa................................................X........................................AA (as the black female's ovary carries AA alleles)

gametes: A, a....................................................................A

F1:..................Aa..................................AA

All guineapigs have black coat. (Phenotypic ratio= black: white= 2:0; Genotypic ratio = AA: Aa = 1:1)

b) If the albino female is mated with the black male, the result will be the same as the albino's ovary carries AA alleles as it was transplanted from a homozygous black female.

The cross will same as that of the above part.

c) If the black female used in the transplant study had a white parent, then its genotype will be Aa.
Then in both cases, the results will change as the ovarian genotype becomes Aa instead of AA.

Aa (male)......................X.....................................Aa (female)

A, a..................................................................A,a

F1:......AA....................Aa................Aa..................aa

Phenotypic ratio= black: albino = 3:1

Genotypic ratio = AA: Aa:aa = 1:2:1

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