Question

Brown fur coloring in mice is controlled by a dominant allele (B) and white fur by its recessive allele (b). Determine the genotypic and phenotypic ratios if a homozygous brown mouse mated with a homozygous white mouse.

Answer 1

A mating between a homozygous brown (BB) and a homozygous white (bb) mouse results in all offspring having the Bb genotype and brown fur, yielding a genotypic ratio of 100% Bb and a phenotypic ratio of 100% brown fur.

Step-by-step explanation:

When a homozygous brown mouse with genotype BB mates with a homozygous white mouse with genotype bb, all offspring will have the genotype Bb, as they receive a B allele from the brown parent and a b allele from the white parent. Since brown fur coloring is dominant (B) over white fur (b), all the offspring will have brown fur. The genotypic ratio is therefore 100% Bb, and the phenotypic ratio is 100% brown fur.

It is important to note that we are not considering any other genes that might affect coat color in mice, such as those causing epistasis, seen in the case of agouti and albino pigmentation outlined in the provided figures. If we were to consider a situation involving epistasis, additional genes would interact with the fur color genes, and we would need more information to determine the new genotypic and phenotypic ratios.