Chapter 12, Problem 11P

The recessive, X-linked z¹ mutation of the Drosophila gene zeste (z) can produce a yellow (zeste) eye color only in flies that have two or more copies of the wild-type white (w) gene. Using this property, tandem duplications of the w⁺ gene called w^+R were identified. Males with the genotype y⁺ z¹ w^+R+spl / Y thus have zeste eyes. These males were crossed to females with the genotype y z¹ w^+R+ spl / y⁺ z¹ w^+R spl⁺ . (These four genes are closely linked on the X chromosome, in the order given in the genotype, with the centromere to the right of all these genes: y = yellow bodies; y⁺ = tan bodies; spl = split bristles; spl⁺ = normal bristles.) Out of 81,540 male progeny of these females, the following exceptions were found:

Class A 2430 yellow bodies, zeste eyes, wild-type bristles

Class B 2394 tan bodies, zeste eyes, split bristles

Class C 23 yellow bodies, wild-type eyes, wild-type bristles

Class D 22 tan bodies, wild-type eyes, split bristles

a.	What were the phenotypes of the remainder of the 81,540 males from the first cross?
b.	What events gave rise to progeny of classes A and B?
c.	What events gave rise to progeny of classes C and D?
d.	On the basis of these experiments, what is the genetic distance between y and spl?