Question

In garden pea plants, the round seed shape (R) is dominant over the wrinkled seed shape (r), and the purple flower (P) is dominant over the white flower (p). A heterozygous round seed purple (RrPp) pea plant is crossed with another heterozygous round seed purple (RrPp) pea plant. Determine the expected phenotypic ratio of the F1 generation.

Answer 1

Crossing RrPp × RrPp gives the classic dihybrid 9:3:3:1 phenotypic ratio:

- 9/16 round, purple
- 3/16 round, white
- 3/16 wrinkled, purple
- 1/16 wrinkled, white

(Reason: Rr × Rr → 3/4 round : 1/4 wrinkled; Pp × Pp → 3/4 purple : 1/4 white; multiply probabilities for combined phenotypes.)