Question

In cats, gene 1 specifies coat color. Allele B leads to a black coat color, while allele b leads to a chocolate coat color. Gene 2 can inhibit coat color. The genotype cc leads to an albino cat, while at least one copy of allele C allows the full color from gene 1 to be expressed. What is the phenotype ratio produced for the following cross: BbCc * BbCc?

Answer 1

The phenotype ratio for the cross BbCc × BbCc in cats, considering the epistasis present in the genes responsible for coat color, is 9 black: 3 chocolate: 4 albino. The gene for color expression is epistatic to the gene for color, and any cat with the cc genotype will be albino regardless of the coat color dictated by the other gene.

Step-by-step explanation:

The phenotype ratio produced for the cross BbCc × BbCc in cats, considering epistasis, is 9 black: 3 chocolate: 4 albino.In the context of epistasis as seen in the coat color of cats, we have two interacting genes. Gene 1 with alleles B and b determines the coat color, with B being dominant for black and b for chocolate. Gene 2 with alleles C and c determines whether the color will be expressed; cc results in albinism, a lack of pigment, overriding Gene 1's color determination. To calculate the phenotypic ratio for the cross of two BbCc cats, we first consider each gene separately and then combine them.

For Gene 1, the possible genotype combinations from Bb × Bb are BB, Bb, and bb, leading to a ratio of 3:1 for black (BB, Bb) to chocolate (bb) if Gene 2 allows color expression. For Gene 2, Cc × Cc yields CC, Cc, and cc, with the last one being epistatic and causing albinism. When crossing both genes, the resultant phenotypic ratio is 9 black (BBCC, BBCc, BbCC, BbCc), 3 chocolate (bbCC, bbCc), to 4 albino (BBcc, Bbcc, bbcc) cats, considering that any genotype with cc results in an albino phenotype.