Question

In the case of incomplete dominance the monohybrid $F_2$ generation will show

• A. Identical genotypic and phenotypic ratio of 3:1.
• B. Genotypic ratio of 1:2:1 and phenotypic ratio of 3:1.
• C. Identical genotypic and phenotypic ratio of 1:2:1
• D. Genotypic ratio of 3:1 and phenotypic ratio of 1:2:1.

Answer 1

Answer: (C)

Incomplete dominance occurs when a dominant allele does not completely mask the expression of recessive allele and the phenotype of progeny shows blended expression of both the alleles. The heterozygote formed in this case has a different phenotype from homozygous for either of the alleles. The phenotype of the $F_1$ generation was intermediate of both the parents. It can be understood by studying the inheritance of flower colour in snapdragon.
Cross: red flower (RR) X white flower (rr)
F1 generation: Rr (pink)

	R	r
R	RR	Rr
r	Rr	rr

$F_2$ Genotypic ratio $=1:2:1$ (RR: Rr: rr)
$F_2$ Phenotypic ratio $=1:2:1$ (Red: Pink: White).