Question

In Drosophila ,vestigial (vg) wings and reduced (rd) bristles are both recessive mutations in Drosophila. vg and rd are both found on chromosome 2, which is depicted in the map below. A female from a homozygous strain of vestigial flies was crossed with a male from a homozygous strain of reduced bristle flies. The F1 hybrids were phenotypically wild-type (long wings and normal bristles). If a female F1 fly is mated with a vestigial male having reduced bristles, what proportion of the progeny would have long wings and normal bristles?

Answer 1

Answer: The answer is: 1/4 of the progeny would have long wings and normal bristles if there is no recombination.

Explanation: If you cross a heterozygous wild type (VvRr) with an homozygous recessive (vvrr) you obtain.

According to segregation law: Gametes 1/2 V, 1/2 v, v

1/2 R, 1/2 r x r

After dfistribution you end up with 1/4 VvRr, 1/4vvRr, 1/4 vvRr, 1/4 vvrr

from this result only 1/4 th ends up with wild type.