Chapter 2, Problem 10P

The dorsal pigment pattern of frogs can be either “leopard” (white pigment between dark spots) or “mottled” (pigment between spots appears mottled). The trait is controlled by an autosomal gene. Males and females are selected from pure-breeding populations, and a pair of reciprocal crosses is performed. The cross results are shown below.

Cross 1:

P: Male leopard $\times$ female mottled

F1: All mottled

F2: 70 mottled, 22 leopard

Cross 2:

P: Male mottled $\times$ female leopard

F1: All mottled

F2: 50 mottled, 18 leopard

a. Which of the phenotypes is dominant? Explain your answer.

b. Compare and contrast the results of the reciprocal crosses in the context of autosomal gene inheritance.

c. In the F2 progeny from both crosses, what proportion is expected to be homozygous? What proportion is expected to be heterozygous?

d. Propose two different genetic crosses that would allow you to determine the genotype of one mottled frog from the F2 generation.