Solution-What are the map distances for the three genes

In the fruit fly, Drosophila melanogaster, a spineless (no wing bristles) female fly is mated to a male that is claret (dark eyes) and hairless (no thoracic bristles). Phenotypically wild-type F1 female progeny were mated to fully homozygous (mutant) males, and the following progeny (1000 total) were observed:

      Phenotypes                 Number Observed

      spineless                              321

      wild-type                               38

      claret, spineless                    130

      claret                                     18

      claret, hairless                      309

      hairless, claret, spineless       32

      hairless                                140

      hairless, spineless                 12

(a) Which gene is in the miIDle?

(b) With respect to the three genes mentioned in the problem, what are the genotypes of the homozygous parents used in making the phenotypically wild-type F1 heterozygote?

(c) What are the map distances for the three genes? A correct formula with the values “plugged in” for each distance will be sufficient.

(d) What is the coefficient of coincidence? A correct formula with the values “plugged in” will be sufficient.

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