In a certain plant, fruit color is affected by an epistatic interaction between two genes. The fruit is red in the presence of at least one dominant allele of either or both gene A or gene B, and white when there are no dominant alleles present. What proportion of the offspring of a cross of AaBb x AaBb plants is expected to be red

15/16 or 93.75%

Explanation:

The proportion of the offspring of the cross expected to be red would be 15/16 or an equivalence of 93.75%.

Red fruit color is conditioned by the presence of A_, B_ or A_B_ alleles. In the absence of both dominant alleles, the condition is white. AaBb was crossed with AaBb.

AaBb   x   AaBb

Progeny' Genotype       Phenotype

1 AABB                               red

2 AABb                               red

2 AaBB                                red

4 AaBb                                 red

1 AAbb                                 red

2 Aabb                                  red

1 aaBB                                  red

2 aaBb                                  red

1 aabb                                   white

Hence, the proportion of the offspring that are expected to be red is 15/16 or 93.75%.

See the attached image for the Punnet's square analysis of the cross.