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 aa or bb).
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.
