Expert: Dana Krempels, Ph.D. - 12/11/2007

Question
I really do appreciate your help.
1.   A fruit fly with a gray body and red eyes (genotype BbPp) is mated with a fly having a black body and purple eyes (genotype bbpp). What offspring, in what proportions, would you expect if the body and eye color genes are on different chromosomes (unlinked)? When this mating is actually carried out, most of the offspring look like the parents, but 3% have a gray body and purple eyes, and 3% have a black body and red eyes. Are these genes linked or unlinked? What is the recombination frequency?

i suppose there wold be 4 different types of offspring. 1/4 would be BbPp gray body and red eyes. 1/4 would be Bbpp gray body and purple eyes. 1/4 would be bbPp black body and red eyes and the last 1/ would be bbpp black body and purple eyes. when the mating is carried out, most of the offspring look like both parents so the recombination frequency is 6%.... is this correct???


Answer
Dear Lorraine,

You're correct.  Six percent of the offspring cohort are recombinants.  You'd have to do a bit more math to determine the map distance between the two linked loci, but I guess that's not part of the question.

Congratulations!  :)

Dana