Question

In incomplete dominance,ratio of red:pink:white is
A)1:2:1
B)1:1:2
C)1:2:2
D)2:2:1

Answer 1

Incomplete dominance occurs when neither of the two alleles is fully dominant nor recessive towards each other. The genotype and phenotype ratio of all spring gives the same ratio for a single trait displaying incomplete dominance between the cross of two F1 hybrids.

Complete answer:
When the dominant allele does not completely cover the effect of a recessive allele. Then this is known as incomplete dominance.here the physical appearance of the organism shows a mixing of both the alleles
Let's learn about incomplete dominance with an example of Snapdragon flower-
-A monohybrid cross between the white colour flowers of Snapdragon and red colour flower of the Snapdragon plant is done
-Consider a pure breed of the red flower has RR pair of alleles and that for the white flower is rr.
-Firstly, there is a cross between true-breeding red flower (RR)and White coloured flower (rr) of Snapdragon. The first-filial generation produce a pink colour flower with Rr pair of alleles
-Then the F1 progeny was self-pollinated which results in the red, pink, and white flowers in the ratio of 1:2:1
-Mendel also gives the same genotype ratio of 1:2: 1in the second-filial generation of the monohybrid cross but the phenotypic ratio changes from 3:1 to 1:2:1. The reason for this difference is the incomplete dominance of the allele R over the allele r. This led to the mixing of colour in flowers.

Additional Information: -There is a major dissimilarity between incomplete dominance and codominance. In codominance, two alleles are present on a gene and both are expressed in the phenotype. A flower will have spots of red and white instead of a uniformly pink flower in the codominance.
-The second filial generation in the incomplete dominance from the heterozygous plant will give the ratio of 1:2:1 having the physical appearance (phenotypic character)of red, White and spotted flowers.
-The AB Type of the human blood group also shows the codominance where both the allele of the blood type A and B are expressed.
So, the correct answer is, "1:2:1".

Note: -For the study of genetics, incomplete dominance is a very important concept because in this the two copies of a gene for a specific trait mixed so that they do not dominate the other.
-A new set of observable character and a new phenotype can be created by the interaction of the genes and the environment.