Final answer:
The genotype Aa BB would be included with the '9' portion of the modified 9-7 epistatic ratio, as it contains at least one dominant allele for both interacting gene pairs, resulting in the expression of the dominant phenotype.
Step-by-step explanation:
Epistasis often results in modified dihybrid phenotypic ratios due to one gene masking the expression of another. In a 9-7 epistatic ratio, we are examining a case where one gene pair (A and B) is interacting, and the presence of a dominant allele in either gene results in the dominant phenotype. Considering the information about epistasis in mice, where the gene for pigment production (C) is epistatic to the gene determining the coat color (A), and given the modified ratio of 9-7, we know that the dominant phenotype is expressed when at least one dominant allele is present in either gene A or B. Therefore, a possible genotype for the phenotype that would be included with the '9' portion of the ratio would be Aa BB, where the presence of at least one dominant allele in both gene pairs leads to the expression of the dominant phenotype.