Chapter 2, Problem 42P

In chickens, the presence of feathers on the legs is due to a dominant allele (F), and the absence of leg feath-ers is due to a recessive allele (f). The comb on the top of the head can be either pea-shaped, a phenotype that is controlled by a dominant allele (P), or a single comb controlled by a recessive allele (p). The two genes assort independently. Assume that a pure-breeding rooster that has feathered legs and a single comb is crossed with a pure-breeding hen that has no leg feathers and a pea-shaped comb. The $F_1$ are crossed to produce the $F_2$. Among the resulting $F_2$, however, only birds with a single comb and feathered legs are allowed to mate. These chickens mate at random to produce $F_3$ progeny. What are the expected genotypic and phenotypic ratios among the resulting $F_3$ progeny?