Question

Epistasis often results in modified dihybrid phenotypic ratios. assume that you obtain one such modified ratio, 9:7, with the gene pairs a and b involved. what would be a possible genotype for a phenotype that would be included with the 9 portion of the modified ratio?

Answer 1

Answer:

The answer is AaBB the genotype for 9 in ratio 9:7.

Explanation:

Epistasis is the interaction that occurs in genes that are located at different loci located on the same chromosome, with the consequence that one gene can mask or suppress the expression of another gene. This means that an epistatic gene appears (gene that manifests itself) and another called hypostatic (non-allelic gene that is inhibited). This type of interaction is the product of genes not alleles.

Answer 2

When two genes (A and B) are involved in a pathway, both are required to make functional products for expression. When there's a presence of recessive allele of either of the two genes, it results in the expression of a mutant phenotype. The normal ratio of a self-crossed dihybrid is 9:3:3:1, but due to epistatic interations of the A and B genes, the ratio gets modified to 9:7. The 9 portions in this ratio will correspond to the A_B_ genotype i.e., (AaBb, AABb, AaBB, AABB).