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

NTA AbhyasNTA Abhyas 2022

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.

Solution:

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).