Question

In cats, gene 1 specifies coat color; allele B leads to black coat while allele b leads to chocolate coat color. Gene 2 can inhibit coat color: 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 phenotypic ratio produced for the following cross: BbCc x BbCc?

Answer 1

The phenotypic ratio for the cross BbCc x BbCc in cats is 9 black:3 chocolate:4 albino, considering that one gene specifies coat color and another can inhibit coat color. This scenario involves epistasis, where the gene responsible for color inhibition masks the expression of the coat color gene when present in a recessive homozygous state.

Step-by-step explanation:

The phenotypic ratio produced for the cross BbCc x BbCc in cats, considering that gene 1 (B) specifies coat color and gene 2 (C) can inhibit coat color, can be calculated using a Punnett square. Given that allele B leads to a black coat, allele b to a chocolate coat, and genotype cc to an albino cat, the cross takes into account epistasis, where gene 2 is epistatic to gene 1. This means gene 2 can mask the expression of gene 1.

To calculate the phenotypic ratio, we need to consider that having at least one copy of allele C allows color expression from gene 1. When we perform the cross BbCc x BbCc, we obtain the following phenotypic ratio: 9 black:3 chocolate:4 albino. This is because the presence of the cc genotype in an offspring results in an albino cat, regardless of the B gene's alleles.