Question

In the fruit fly Drosophila, there is a dominant gene for normal wing shape and its recessive allele for dumpy wings. At another gene locus on the same chromosome, there is a dominant gene for tan body color and its recessive allele for ebony body color. A male that is homozygous for both dominant alleles is crossed with a female that is homozygous for both recessive alleles. What percentage of the F1 flies are expected to be heterozygous at both gene loci? ( Enter the number only without the percent sign. For example, enter 100% as 100 and enter 12.5% as 12.5 )

Answer 1

If we name the gene for wing shape with A

Genotype for the normal wing shape would be either AA or Aa and recessive genotype for dumpy wings would be aa. If we name the other gene for body color with B, then  

genotype for tan body color would be BB or Bb and for ebony body color bb.

If we cross a male homozygous for both dominant alleles with a female homozygous for both recessive alleles:

P: AABB  x aabb

F1: AaBb

All of the offspring would be heterozygous at both gene loci.

So, the answer is 100.