Question

In a cross between homozygous wild-type drosophila and yellow-bodied males of all of the f1's were phenotypically wild-type. the f2 generation (resulting from matings of the f1's) had 356 wild-type offspring. however, all 240 females were wild-type and of the 239 males, 116 were wild-type and 123 were yellow-bodied. how is the yellow-bodied trait inherited?

Answer 1

The yellow-bodied trait has a chromosomal basis in sex and is only inherited in X-linked genes. I know this because a single copy of the mutant allele could produce the yellow body since males have only 1 X chromosome and no wild-type allele can mask it. But females could only have yellow bodies if both their X chromosomes carried the recessive allele, which would be impossible in the F2 generation because they would receive either one recessive allele from the father or the wild-type allele.