In fruit flies, red eyes (pr+_) are dominant to purple eyes (prp) and normal wings (vg+_) are dominant to vestigial wings (vgv). the genes are located on the same chromosome. a pure-breeding red-eyed fly with vestigial wings was crossed with a pure-breeding purple-eyed fly with normal wings. all of the f1 progeny had a wt phenotype. the recombination frequency between the two genes is 15%. if an f1 individual were test crossed, what percentage of the progeny would you expect to have the wt phenotype?

7.5%

Explanation:

The genes vg+/vg and pr+/pr are linked.

A pure-breeding red-eyed fly with vestigial wings was crossed with a pure-breeding purple-eyed fly with normal wings.

This cross can be written down as:

x

The wild-type F1 would be:

They are test crossed with a homozygous recessive individual that can produce only one type of gamete: pr vg

The F1 flies will produce 4 types of gametes:

Each time recombination happens, the two possible recombinant gametes are generated. Because the recombination frequency between the two genes is 15% altogether, each recombinant gamete will appear with half that frequency, 7.5% of the times.

The pr+ vg+ recombinant gamete will be produced with a frequency of 7.5%, and when it's combined with the pr vg gamete from the test cross individual, it will give rise to offpring with WT phenotype.

so whats the answer