N Drosophila, the Autosomal Recessive Pr and Cn Mutations Cause

Multiple Choice

n Drosophila, the autosomal recessive pr and cn mutations cause brown and bright-red eyes, respectively (wild-type flies have brick-red eyes) .Flies who are homozygous recessive at both pr and cn have orange eyes.A female who has wild-type eyes is crossed to an orange-eyed male.Their progeny have the following distribution of eye colors:
$$\begin{array} { | l | r | } \hline \text { wild-type } & \text { 8 } \\\hline \text { brown } & 241 \\\hline \text { briphit-red } & 239 \\\hline \text { orarnge } & \underline{12} \\\hline & 500 \\\hline\end{array}$$
-What is the map distance between the pr and cn genes?

A) 20 m.u.
B) 2 m.u.
C) 4 m.u.
D) 46 m.u.
E) 8 m.u.