In Drosophila, the Genes Y, F, and V Are All

Multiple Choice

In Drosophila, the genes y, f, and v are all X-linked. Females who are homozygous for recessive alleles of all three genes (y f v / y f v) are crossed to wild-type males. The resulting trihybrid F1 females are testcrossed. The F2 are distributed as follows:

$$\begin{array} { | l | r | } \hline y f v & 3210 \\\hline y f v ^ { + } & 72 \\\hline y f ^ { + } v & 1024 \\\hline y f ^ { + } v^ + & 678 \\\hline y ^ { + } f v & 690 \\\hline y ^ { + } f v ^+ & 1044 \\\hline y ^ { + } f ^+ v & 60 \\\hline y ^ { + } f ^+ v^ + & 3222 \\\hline & 10,000 \\\hline\end{array}$$

-Which of the following linkage maps correctly shows the order and distance between the y, f, and v genes?

A) f--35 m.u.--y--15 m.u.--v
B) f--22 m.u.--y--15 m.u.--v
C) y--35 m.u.--f--22 m.u.--v
D) y--22 m.u.--v--15 m.u.--f
E) y--15 m.u.--v--22 m.u.--f