Question

A purple-flowered pea plant is crossed with a white-flowered pea plant. All the F1 plants produced purple flowers. When the F1 plants are allowed to self-pollinate, 401 of the F2s have purple flowers and 131 have white flowers. What are the genotypes of the parental and F1 generation plants?

Answer 1

Answer:

Parentals: PP (purple) and pp (white)

F1: Pp (purple)

Explanation:

When the two parental plants of differing phenotypes (purple or white flowers) cross, the F1 is 100% purple. This result suggests that the parentals were true breeding (homozygous), with purple flowers being the dominant allele.

When the F1 self pollinates, the F2 shows proportions very similar to 3/4 purple and 1/4 white (401/532 ≅ 3/4 and 131/532 ≅ 1/4). The 3:1 phenotypic ratio is typical of the offspring resulting from a cross between two heterozygous individuals.

The results make sense if the genotypes of the different generations are:

Parentals: PP (purple) X pp (white)

F1:                          Pp (purple)

F2:  1/4 PP, 2/4 Pp, 1/4 pp