Question

9:3:3:1 ratio is modified to 9:7 ratio due to
(a)Complementary gene
(b)Epistatic gene
(c)Hypostatic gene
(d)Supplementary gene

Answer 1

Hint: An interaction of two dominant non-inter allelic genes in which each gene has its effect but when come together to interact a new trait is developed. Here 9:3:3:1 is the Mendelian ratio.

Complete answer:
The complementary gene is an interaction of two dominant non-inter allelic genes in which each gene has its effect but when come together to interact a new trait is developed and the Mendelian ratio 9:3:3:1 is changed to 9:7 due to the complementation of both genes.

Additional Information: In complementary genes, the dihybrid ratio of 9 : 3 : 3: 1 is modified to 9:7 as follows:-
When one gene inhibits the expression of others; the dominant alleles of one gene (A) in homozygous and heterozygous (AA, Aa) condition and homozygous recessive alleles bb of another gene (B) produce the same phenotype. Here, the rest genotypes produce contrasting phenotypes; thus only two phenotypes. The resultant ${ F }_{ 2 }$ ratio is 13: 3. The non-allelic gene interaction in which the trait is governed by duplicate genes for which the presence of the single dominant gene is enough to produce the dominant trait, the dihybrid ratio becomes 15: 1. Here, all genotypes carrying a single/multiple dominant genes show a dominant phenotype. Dominant epistasis is the non-allelic gene interaction where the presence of one dominant gene masks the expression of another dominant gene, and the dihybrid ratio becomes 12 : 3: 1. Complementary genes are the non-allelic genes that have their independent effect but produce a new trait when their dominant forms are present together. A hybrid cross of complementary genes gives 9: 7 as its phenotypic ratio.
So, the correct answer is, “complementary gene”.

Note: -Epistasis: Mutations with different phenotypes. However, in the ${ F }_{ 2 }$, a 9:3:4 phenotypic ratio is produced. This kind of interaction is called epistasis, which means “standing on”; in other words, an allele of one gene masks the expression of the alleles of another gene.
-Supplementary genes (9 : 3: 4 ratio): Supplementary genes are two independent pairs of dominant genes and one dominant gene will produce its effect whether the other is present or not.