Typical ratios resulting from epistatic interactions in dihybrid crosses would be a) 9: 3: 3: 1, 1: 2: 1 b) 1: 1: 1: 1, 1: 4: 6: 4: 1 c) 9: 3: 4, 9: 7 d) 1: 2: 2: 4: 1: 2: 1: 2: 1, 1: 2: 1 e) 3: 1, 1: 1

C) 9:3:4, 9:7

Explanation:

When there are no epistatic interactions, the expected phenotypic ratio of the offspring resulting from a dihybrid cross is 9:3:3:1:

9 A_B_ : 3A_bb : 3 aaB_ : 1 aabb

If there is epistasis, the ratios change, but the new ratios will be the addition of the ratios of two or more genotypes. For example, in the recessive epistasis (9:3:4), the recessive allele of one gene (let's say aa) mask the expression of the dominant allele of the other gene (in this case, B), so two different genotypes will have the same phenotype, and therefore their ratios will combine.

In the 9:3:4 epistasis, the phenotypic ratios 9:3:3:1 change to: 9 A_B_ : 3 A_bb : 4 aaB_/aabb.

On the other hand, in the epistasis due to complementary genes (9:7) at least one dominant allele of each gene needs to be present to produce a certain phenotype. Otherwise, the phenotype will be different. For example, a plant with A_B_ genotype will have colored flowers, and a plant with the genotypes A_bb, aaB_ or aabb will have white flowers. The new ratio would be 9 colored : 7 white.

it is a limiting nutrient limited by a single nutrient in the ecosystem, & the single goes very slow.