Question

Phenotypic and genotypic ratio in F2 generation in incomplete dominance is-
A. 1:2:1 and 1:2:1
B. 9:6 and 1:2:1
C. 9:6 and 3:1
D. 9:3:3:1 and 1:2:1:2:4:1:1:2:1:2:1

Answer 1

Hint: Incomplete dominance is a type of intermediate inheritance in which the effect of the dominant allele is diluted by the recessive allele. The dominant allele does not mask the effect of the recessive allele completely whereas a blending of the effects of both the allele is shown.

Complete answer:
This term was introduced by the German botanist Carl Correns by conducting an experiment on the Four o’clock flower. In this condition, a heterozygous individual does not show the effect of the dominant allele rather the phenotypes of dominant and recessive alleles are blended together and show an intermediate of both the phenotypes. This is also called partial dominance or semi dominance or intermediate inheritance because the dominant allele does not completely dominate the recessive allele. Two alleles are expressed together in the heterozygous and thus it plays an important role in the gene study.
Some famous examples of this inheritance are- the ABO blood group system in humans, hair pattern (curly or wavy) in humans, the color of the flower in roses and Mirabilis jalapa, etc.
The phenotypic ratio in the F2 generation differs from the original ratio due to this incomplete inheritance pattern. This can be explained through a Punnett square.

The phenotypic ratio in this is similar to the genotypic ratio i.e, 1:2:1. The first number depicts the dominant trait while the last depicts the recessive trait in the ratio. The middle number indicates the blending result of both alleles. The normal phenotypic ratio in F2 generation is 3:1 and the genotypic ratio is 1:2:1.

Option A: In incomplete dominance, a cross of two F1 hybrids results in the production of a similar genotypic and phenotypic ratio- 1:2:1.

Hence, the correct answer is option (A)

Note: Punnett square is a square diagram used to predict the genotypic ratio in a cross or breeding experiment. This square is also used in the phenotypic ratio in the case of incomplete dominance because the alleles are simply not dominant or recessive and the phenotype is an intermediate. It is used to determine the statistical data of each genotype.