Final answer:
The genotype of the albino fox is 'Aacc' and the red fox must have a genotype with at least one dominant 'C' allele, like 'AaCC' or 'AaCc', to prevent albinism in their offspring due to the epistatic effect of the C gene over the A gene.
Step-by-step explanation:
In discussing epistasis using foxes or mice as examples, we are referring to a situation in genetics where the effect of one gene (the epistatic gene) masks or modifies the effect of another gene (the hypostatic gene). Specifically, in the coat coloration of foxes, similar to the phenomena observed in mice, the albinism trait is caused by the recessive allele 'c' of the C gene, which is responsible for pigment production. This allele is epistatic to the genes determining the actual color (A gene), such as the agouti or solid color. Thus, for no pups to be albino from a cross of a red fox must imply that neither parent fox contributed the recessive 'cc' genotype.
If the red fox and the albino fox breed and no offspring is albino, it is likely that the albino parent was of genotype 'Aacc' and the red fox was of genotype 'AaCC' or 'AaCc'. Since albino offspring were not produced, it can be concluded that the red fox carries at least one dominant 'C' allele, preventing the expression of albinism, as an albino phenotype would only appear in the presence of a 'cc' combination from both parents.