Mouse pigmentation is subject to epistasis of the B alleles by the d alleles. B (black) is dominant over b (brown), and D is dominant over d . Homozygous d is epistatic to the black and brown genes. Given this information, what will result from a F₁cross between two mice? A) 9/16 black, 3/16 brown, 4/16 white B) 9/16 white, 3/16 brown, 4/16 black C) 9/16 black, 6/16 brown, 1/16 white D) 9/16 white, 6/16 brown, 1/16 black E) all black mice

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In this scenario, the presence of homozygous recessive d alleles (dd) is epistatic to the B and b alleles, meaning it can mask their effects and result in white mice regardless of the B/b allele combination. Assuming both parents are heterozygous for both genes (BbDd), a Punnett square analysis shows that 9/16 of the offspring will have at least one D allele and one B allele (black), 3/16 will have at least one D allele and be homozygous for b (brown), and 4/16 will be homozygous for d (dd) and thus white, regardless of the B/b alleles.

Mouse Pigmentation Is Subject to Epistasis of the B Alleles