Answer:
e. Epistatic interaction of the two genes
Explanation:
The 9:7 ratio is typical of the Duplicate Recessive Epistasis.
The expected phenotypic ratiio of the offsrping of a dihybrid cross is:
9 A_B_
3 A_bb
3 aaB_
1 aabb
In the Duplicate Recessive Epistasis, the A_bb, aaB_ and aabb individuals all have the same phenotype, making for the ratio 9:7. What those three genotypes have in common is that in all of them at least one of the two genes is homozygous recessive (either <em>aa</em> or <em>bb</em>).
This usually happens one the products of genes A and B are enzymes of the same metabolic pathway.
Whenever both A and B are present, the pathway can produce the final product and a certain phenotype. However, if any of the dominant alleles is missing, the enzyme is not produced and therefore the final product of pathway is not produced, giving the other phenotype.
