A homozygous claret ( ca, claret eye color), curled ( cu, upcurved wings), flute

Question

A homozygous claret (ca, claret eye color), curled (cu, upcurved wings), fluted (fl, creased wings) fruit fly is crossed with a pure-breeding wild-type fly. The F1 females are testcrossed with the following results:

            fluted                                                      4

            claret                                                   173

            curled                                                  26

            fluted, claret                                        24

            fluted, curled                                      167

            claret, curled                                           6

            fluted, claret, curled                            298

            wild-type                                             302

a.         Draw a genetic map of the three genes. Show order and distances between them.

b.         Is there any crossover interference? If yes, how much?

Explanation / Answer

Answer

between fluted and claret 100(175+167+4+6)/1000 = 35.2cM and distance between claret and curled would be 100(26+24+4+6)/1000= 6cM.

gene map would look like this

f....35.2cM.........cl...6cM....cu

b) Yes there is a crossover interference. The recombination frequency of f and cl is 0.352 and between cl and cu is 0.06. so, we expect a percentage of double recombinants of

100*(0.352x0.064) = . 2.1

So, 2.1% of 1000 would be 21 double recombinants.

We should get 21 double recombinants but we get only 10 double recombinants. So, coefficient coincidence (C.O.C) is 10/21=0.47

so, interference is calculated to be 1-C.O.C

so, interference is 1-0.47 = 0.53.

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