Question

A dihybrid ratio of 1:4:6:4:1 is obtained instead of 9:3:3:1. This is an example of
A. Complementary gene
B. Supplementary gene
C. Polygenic inheritance
D. Incomplete dominance

Answer 1

Hint:-Dihybrid cross is a cross between two different lines/genes that differ in two observed traits. Mendel stated that between the alleles of both these loci there is a relationship of completely dominant - recessive traits which result in the expression of the traits in the progeny.

Complete answer:
Complementary genes are the genes that are present on separate loci and interact together to produce dominant phenotypic character, but neither of them if present alone can express itself are called complementary genes. F2 generation of 9:7 ratio of progeny is obtained with these genes. It is also called the modified Mendel dihybrid ratio. A pair of non-allelic genes, in which one produces its effect independently in the dominant state while the dominant allele of the second gene is without any independent effect but modifies the effect of the former to produce a new trait is called Supplementary genes. in the F2 generation, a 9:3:4 ratio of progeny is obtained with these genes. It is also a modified Mendel dihybrid ratio.
Inheritance of a character that has the presence of more than one gene in the population is called polygenic inheritance. These dominant alleles have a cumulative effect and are called Polygenes. in the F2 generation 1:4:8:4:1 dihybrid ratio is obtained instead of the usual 9:3:3:1 Mendel dihybrid ratio. Dominant allele does not completely mask the effects of a recessive allele resulting in phenotype with a blend of both alleles. It is called incomplete dominance or partial dominance.
Thus, the right option is C.

Note:- Human skin colour and eye color, height, weight, and intelligence, and kernel color of wheat all are examples of polygenic (multiple genes) inheritances.