Suppose that pigmentation of a Labrador retriever's fur is subject to epistasis of the B alleles by the e alleles. B (black) is dominant over b (chocolate brown). E is dominant over E.Homozygous e is epistatic to the black and chocolate-brown genes. Given this information, what will result from a F₁ dihybrid cross between two dogs?

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In a dihybrid cross involving epistasis, where the presence of two e alleles (ee) masks the expression of both B and b alleles, the phenotypic ratio deviates from the typical 9:3:3:1 seen in Mendelian dihybrid crosses. Here, ee individuals will be yellow regardless of their B/b genotype, leading to a 9 (black): 3 (brown): 4 (yellow) ratio, assuming both parents are heterozygous for both genes (EeBb x EeBb).

Suppose That Pigmentation of a Labrador Retriever's Fur Is Subject