Chapter 5, Problem 15PDQ

Another cross in Drosophila involved the recessive, X-linked genes yellow (y), white (w), and cut (ct). A yellow-bodied, white-eyed female with normal wings was crossed to a male whose eyes and body were normal but whose wings were cut. The F₁ females were wild type for all three traits, while the F₁ males expressed the yellow-body and white-eye traits. The cross was carried to an F₂ progeny, and only male offspring were tallied. On the basis of the data shown here, a genetic map was constructed.

1. (a) Diagram the genotypes of the F₁ parents.
2. (b) Construct a map, assuming that white is at locus 1.5 on the X chromosome.
3. (c) Were any double-crossover offspring expected?
4. (d) Could the F₂ female offspring be used to construct the map? Why or why not?