A pure line of Guinea pigs with genotype A/A;b/b is crossed to a pure line with genotype a/a;B/B.The F₁ male and female Guinea pigs are crossed to each other to generate the F₂.What proportion of the F₂ individuals are the result of a recombinant egg being fertilized by a recombinant sperm?

Question

Quizplus · Accepted Answer

The gametes from the A/A;b/b parent are AB and Ab and those from the a/a;B/B parent are aB and AB. The F1 offspring are all Aa;Bb, the result of the cross AB/aB x Ab/AB. When the F1 individuals are crossed to each other, the potential gametes are AB, Ab, aB, and ab. The expected genotypic ratio among the offspring is 9:3:3:1 for A;B/ab:A;b/ab:aa;B/ab:aa;bb. Among these, only the A;b/ab and aa;B/ab would be the result of a recombinant egg fertilized by a recombinant sperm, which accounts for 4/16 or 1/4 of the expected offspring. Therefore, the correct answer is C.

A Pure Line of Guinea Pigs with Genotype A/A;b/b Is