Question

You cross a p+/v+ p+/v+ male drosophila to a p-/v- p-/v- and obtain the F1 hybrid. Now you cross the F1 male with double recessive female. What will be the recombination phenotype in F2?

(a) p+/v+ p-/v- only

(b) p+/v+ p-/v- and p-/v- p-/v-

(c) p+/v+ p-/v- and p-/v- p-/v- also p+/v- p-/v- and p-/v- p-/v-

(d) p+/v+ p-/v- and p-/v- p-/v- also p-/v+ p-/v- and p-/v- p-/v-

The question was posed to me in quiz.

This key question is from Linkage and Crossing Over topic in portion Genetic Recombination of Cytogenetics

Answer 1

Correct answer is (b) p+/v+ p-/v- and p-/v- p-/v-

The best explanation: In male drosophila recombination is absent thus there can’t be formation of p+/v- and p-/v+ gametes at all. This can however be formed in case we use female F1 for the test cross.