Chapter 2, Problem 39P

A cross between a spicy variety of Capsicum annum pep-per and a sweet (nonspicy) variety produces F1 progeny plants that all have spicy peppers. The $F_1$ are crossed, and among the $F_2$ plants are 56 that produce spicy peppers and 20 that produce sweet peppers. Dr. Ara B. Dopsis, an expert on pepper plants, discovers a gene he designates Pun1 that he believes is responsible for spicy versus sweet flavor of peppers. Dr. Dopsis proposes that a dominant allele P produces spicy peppers and that a recessive mutant allele p results in sweet peppers.

a. Are the data on the parental cross and the $F_1$ and $F_2$ consistent with the proposal made by Dr. Dopsis? Explain why or why not, using P and p to indicate probable genotypes of pepper plants.

b. Assuming the proposal is correct, what proportion of the spicy $F_2$ pepper plants do you expect will be pure-breeding? Explain your answer.