In the Fruit Fly, Drosophila Melanogaster, a Spineless (No Wing

question 26

Essay

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: $$\begin{array} { l r } \text { Phenotypes } & \text { Number Obsreved} \\\text { spineless } & 321 \\\text { wild } & 38 \\\text { claret, spineless } & 130 \\\text { claret } & 18 \\\text { claret, hairless } & 309 \\\text { hairless, claret, spineless } & 32 \\\text { hairless } & 140 \\\text { hairless, spineless } & 12\end{array}$$ a) Which gene is in the middle?
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 between 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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