NEET BIOLOGY

Detailed explanation-1: -In sweet pea the epistatic interaction between the genes for purple and white colour produced the 2 colours in the ratio 9:7.

Detailed explanation-2: -The F1 generation has all purple flowers ( CcPp). When a purple flower is self-fertilized it gives 9 purple flowers and 7 white flowers making the ratio 9:7: Thus the non-mendelian complementary genes show a 9:7 phenotypic ratio.

Detailed explanation-3: -The modified 9:7 ratio may, therefore, be obtained when two genes act together in the same biochemical pathway, and when their loss of function phenotypes are indistinguishable from each other or from the loss of both genes. There are also other possible biochemical explanations for complementary gene action.

Detailed explanation-4: -In plants that have at least one dominant allele of each of the two genes, we get the dominant phenotype; otherwise, we get the recessive phenotype. Therefore, a 9:7 ratio has been seen in the F2 generation. A dihybrid cross has a 9:7 Mendelian ratio prevailing epistasis.

Detailed explanation-5: -The complementary gene is a interaction of two dominant non inter-allelic gene in which each gene have its own 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 complementation of both genes.