Dr.Disney has been raising exotic fruit flies for decades.Recently, he discovered a strain of fruit flies that in the recessive condition have baby blue eyes that he designates as bb.He also has another strain of fruit flies that in the recessive condition have pink wings that are designated as pw.He is able to establish flies that are homozygous for both mutant traits.He mates these two strains with each other.Dr.Disney then takes phenotypically wild-type females from this cross and mates them with double recessive males.In the resulting testcross progeny he observes 500 flies that are of the following make-up: What is the relationship with respect to location between the two genes?

Question

Dr.Disney has been raising exotic fruit flies for decades.Recently, he discovered a strain of fruit flies that in the recessive condition have baby blue eyes that he designates as bb.He also has another strain of fruit flies that in the recessive condition have pink wings that are designated as pw.He is able to establish flies that are homozygous for both mutant traits.He mates these two strains with each other.Dr.Disney then takes phenotypically wild-type females from this cross and mates them with double recessive males.In the resulting testcross progeny he observes 500 flies that are of the following make-up:  What is the relationship with respect to location between the two genes?

Quizplus · Accepted Answer

The testcross progeny shows that there are four different gamete combinations that result from the double recessive male and wild type female mating. The gamete combinations are e a b c, e a b c, e a B C, and e a B C. This suggests that the two genes are linked, as the recombinant gamete combinations (e a b C and e a B c) are present in a lower frequency than the parental gamete combinations. The map distance between the two genes can be calculated as (number of recombinant progeny/total number of progeny) x 100 = (19+3)/500 x 100 = 4.4%. This converts to a map distance of 16.6 cM, indicating that the two genes are somewhat close together on the same chromosome. Therefore, the best answer choice is D.

DrDisney Has Been Raising Exotic Fruit Flies for Decades