Question

A dihybrid ratio of 1:4:8:4:1 is obtained instead of 9:3:3:1. This is an example of
A. Complementary genes
B. Supplementary genes
C. Polygenic inheritance
D. Pleiotropic genes

Answer 1

Hint: Human skin color represents the kind of polygenic inheritance. In the polygenic inheritance the cross occurred between the two individuals which are heterozygous for the three alleles and obtained the phenotypic ratio. And the trait present in the polygenic is influenced by more than one gene that helps to distribute the function of the human body such as skin color and height.

Complete answer:
Complementary genes are those genes that present on the separate loci and interact together to obtain the dominant phenotype characters. Due to the complementary genes ${F_1}$ generation produced a 9:7 ratio of the progeny and modified by the Mendel experiments. The Mendel experiment that is based on the dihybrid ratio and B. supplementary of the genes. And a pair of non-allelic genes that obtained the independent effect on the dominant phenotype and on the other side dominant phenotype without any independent effect but is able to modify the effect of previous trait to produce new traits also known as supplementary genes.
But in the case of ${F_2}$ generation 9:3:4 ratios are obtained also from the Mendel experiment results. And polygenic inheritance characters obtained due to the presence of more than one gene present in it. And polygenic inheritance known as quantitative inheritance. Quantitative inheritance alleles have cumulative effects because genes are involved that’s why they are called polygenes.And obtained the 1:4:8:4:1.

Therefore the correct option is (C).

Note: Pleiotropic is the process in which the ability of a gene to produce more than one phenotype in an organism. But in the pleiotropic genes are not essential traits are equally influenced. In this the effect of the gene is more evident in case of less evident traits and one traits in case of other traits.