Question

Define – Incomplete dominance.
If a red flowered Mirabilis jalapa plant is crossed with a white flowered plant, what will be the phenotypic ratio in F2 generation? Show it by a chart.

Hint:

In incomplete dominance, heterozygotes show a blended trait; use Punnett square for F2 ratios.

Answer 1

i. Incomplete Dominance: A genetic phenomenon where neither allele is completely dominant, resulting in an intermediate phenotype in heterozygotes (e.g., pink flowers in Mirabilis jalapa from red and white parents).

ii. F2 Phenotypic Ratio:
Let red flower allele = R, white flower allele = r.
- Parents: Red (RR) × White (rr) → F1: Pink (Rr).
- F1 self-cross: Rr × Rr.

Punnett Square:

	R	r
R	RR (Red)	Rr (Pink)
r	Rr (Pink)	rr (White)

 F2 Phenotypic Ratio: 1 Red : 2 Pink : 1 White

Answer: i. Intermediate phenotype in heterozygotes; ii. 1:2:1 (Red : Pink : White).