The recessive, X-linked z1mutation of the Drosophilagene zeste (z) can produce a yellow (zeste) eye coloronly in flies that have two or more copies of the wildtype white (w) gene. Using this property, tandem duplications of the w+ gene called w+Rwere identified.Males with the genotype y+ z1w+R spl+ / Y thus havezeste eyes. These males were crossed to females withthe genotype y z1 w+R spl / y+ z1 w+R spl+. (These fourgenes are closely linked on the X chromosome, in theorder given in the genotype, with the centromere tothe 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 bristlesClass B 2394 tan bodies, zeste eyes, split bristlesClass C 23 yellow bodies, wild-type eyes, wild-type bristlesClass D 22 tan bodies, wild-type eyes, split bristlesa. What were the phenotypes of the remainder of the81,540 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 geneticdistance between y and spl?
The recessive, X-linked z
1
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 wildtype white (w) gene. Using this property, tandem duplications of the w+ gene called w+R
were identified.
Males with the genotype y
+ z
1
w+R spl+ / Y thus have
zeste eyes. These males were crossed to females with
the genotype y z
1 w+R spl / y+ z
1 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
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?
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