Question

What is the phenotypic ratio in the F₂ generation from selfing heterozygous snapdragons (Rr × Rr) showing incomplete dominance?

Options

• 2 Red : 2 White

• 3 Red : 1 White

• 1 Red : 1 Pink : 1 White

• 1 Red : 2 Pink : 1 White

Answer 1

The F₂ phenotypic ratio is 1 Red : 2 Pink : 1 White. This 1:2:1 ratio is the defining characteristic of incomplete dominance and differs fundamentally from the 3:1 phenotypic ratio observed in complete dominance. The ratio directly corresponds to the genotypes: 1 RR (red), 2 Rr (pink), and 1 rr (white). Notably, the phenotypic ratio equals the genotypic ratio in incomplete dominance, which is NOT the case in complete dominance.