Question

The phenotypic and genotypic ratio in the F2 generation in incomplete dominance is
A) 1:2:1 and 1:2:1
B) 3:1 and 1:2:1
C) 9:6 and 3:1
D) 9:3:3:1 and 1:2:1:4:1:1:1:1:2:1

Answer 1

Hint: Incomplete dominance occurs when the dominant allele is not completely dominant over the recessive allele. This results in the blending of both the alleles. Incomplete dominance is seen in the colour of flowers of several plants.

Complete answer:
To solve this question, we must know about the cross in incomplete dominance.
Incomplete Dominance: It is the condition in which one allele is not completely dominant over the other. This leads to a completely new phenotype which is different from both the parents. For example-

When the purple flower of pea (PP) is crossed with white flowers of pea(pp).
F1 generation – PP X pp, it will yield Pp which are pink in colour as a result of incomplete dominance.
In F2 generation: Pp X Pp, it will be represented as

	P	p
P	PP (purple)	Pp(pink)
p	Pp (Pink)	pp(white)

The phenotypic ratio is the ratio of physically appearing characters. In this case colour is the phenotype. So the ratio obtained is 1:2:1 (1purple: 2pink :1white)

The genotypic ratio is the ratio of gene combination in an organism. In this case, the genotypic ratio is 1:2:1 (1PP:2Pr:1pp)

In case of complete dominance, the phenotypic and genotypic ratio in Mendelian monohybrid cross in which one allele is completely dominant over the other is 3:1 and 1:2:1.

In case of dihybrid cross, the phenotypic and genotypic ratio is 9:3:3:1 and 1:2:1:4:1:1:1:1:2:1. which one allele is completely dominant over the other.

Hence, the correct answer is option (A).

Note: Gregor Mendel is known as Father of Hereditary. He was the one to perform cross in the pea plant and discovered the laws of Independent assortment, law of dominance and law of segregation based on the results obtained from the cross.