Question

A modified dihybrid mendelian ratio of 9:3:4 indicates
A. Supplementary genes
B. Complementary genes
C. Lethal genes
D. Epistatic genes

Answer 1

Hint: Mendelian ratio, is the ratio of the Progeny with the particular Phenotypes or genotypes, expected in accordance with the Mendel law, among the offspring of the mating, are specified to as genotype or phenotype.

Complete answer:
Supplementary genes are the genes of modified dihybrid ratio, these are the pair of non- allelic genes, where one allele produce it’s an independent effect in the dominant state, while the dominant allele of the second gene among the non- allelic genes, do not have any independent effect, but it able to modify the effect of the first one, in order to produce new trait, these are called as supplementary genes, in the F2 generation, these supplementary genes are responsible for the formation of with the ratio of 9:3:4.
Complementary genes: In this type, two genes are present on the separate locus, where their interactions result in the dominant Phenotype. If there are no interactions, neither of the genes do produce dominant characters, so they are called Complementary genes, the ratio obtained in F2 generation is 9:7.
Lethal genes: These are the genes that are present on the Homozygous chromosome, where they cause the death of the individual, in the F2 generation, the progeny obtained from the lethal genes are 2:1.
Epistatic genes: In this type, one gene masks the function of another gene, and the processing is called epistasis, and the ratio of progeny in F2 generation is 12:3:1.

So the answer is Supplementary genes.

Note:
Genetic analysis is the thing which helps to identify the genes and their interactions, in order to determine the particular biologic property, Usually two interacting genes produce the modified dihybrid ratio, these interactions are of various types, which produce a different type of modifications.