Question

Question 1: In Drosophila melanogaster (fruit fly) white eye color (w) and stubby body shape (s) are encoded by two mutant alleles on the X chromosome and are recessive to red eye (W) and full body (S). A heterozygous female is crossed to a white eyed and stubby body male. These two genes on the X chromosome are completely linked.
What are the genotypes of both parent flies (2pts)
What are all the potential phenotypes and genotypes of the F1 progeny (10pts)


Question 2: A homozygous dominant red eye (W) fruit fly with full length wings (V) is crossed to a homozygous recessive white eyed (w) male with vestigial sized wings (v). Eye color gene (red/white) is on the X chromosome and wing size gene (full or vestigial) is on chromosome 2.



What are the genotypes of the parental cross (2pts)
Write out a list of genotypes and phenotypes of the F1 offspring. (4pts)
If the F1 offspring are self-crossed what would the phenotypes and genotypes of the F2 males be? (12pts)

Answer 1

Answer:

A female Drosophila of unknown genotype was crossed with a white-eyed male fly, of genotype (w = white eye allele is recessive, w+= red-eye allele is dominant.) Half of the male and half of the female offspring were red-eyed, and half of the male and half of the female offspring were white-eyed.If the trait is dominant, one of the parents must have the trait. Dominant traits will not skip a generation. If the trait is recessive, neither parent is required to have the trait since they can be heterozygous.The female fly had to be heterozygous, Xw+ Xw.

Explanation: