Question

The genes a, b, and c, are linked on chromosome 3 in Drosophila melanogaster. You testcross a triply heterozygous female fly (she looks wild type) and obtain the following phenotypes among the progeny: abc 23 +++ 22 a++ 49 +bc 46 ab+ 420 ++c 435 a+c 3 +b+ 2 1000

A) Draw the combination of the wild-type and/or mutant alleles on each homolog of chromosome 3 for the triply heterozygous mother fly. (the order of alleles is not important for this part of the question)

B) Which phenotypic classes represent double crossovers?

C) Which gene is in the middle?

D) Draw a map of this chromosome showing the distances between each gene. Please show all of the work required to make this map (don’t make assumptions and skip anything).

E) Do you think there is crossover interference? Explain why or why not.

Answer 1