Chapter 5, Problem 12P

On the $\text{DrosophilaX}$ chromosome, the dominant allele $\text{y+}$ produces gray body color and the recessive allele y producesyellow body. This gene is linked to one controlling full eye shape by a dominant allele $\text{lz+}$ and lozenge eye shape with arecessive allele $\text{lz}$. These genes recombine with a frequency of approximately $\text{28\%}$. The $\text{Lz}$ gene is linked to gene F controlling bristle form, where the dominant is long bristlesand the recessive is forked bristles. The $\text{Lz}$ and F genes recombine with a frequency of approximately $\text{32\%}$.

a. Using any genotypes you choose, design two separatecrosses, one to test recombination between genes Y and $\text{Lz}$ and the second between genes $\text{Lz}$ and F. Assume $\text{1000}$ progeny are produced by each cross, and give thenumber of progeny in each outcome category. (In setting up your crosses, remember that $\text{Drosophila}$ males do not undergo recombination.)

b. Can any cross reveal genetic linkage between gene Y and gene F? Why or why not?

c. Why is “independent assortment” the genetic term thatbest describes the observations of a genetic cross between gene Y and gene F?