Question

In horses, some of the genes for hair color are incompletely dominant. Phenotypes are brown, white, and yellow-tannish called palomino. Brown hair is homozygous dominant, white hair is homozygous recessive, and palomino is heterozygous. What are the genotype and phenotype ratios for a brown female and a palomino male?

Answer 1

When crossing a homozygous dominant brown horse (BB) with a heterozygous palomino horse (Bb), the offspring will have a 1:1 phenotypic ratio of brown to palomino, which corresponds to a 1:1 genotype ratio of BB to Bb due to the incomplete dominance of the hair color genes.

Step-by-step explanation:

In horses, when considering hair color genetics, incomplete dominance is a type of inheritance in which one allele is not completely dominant over another, leading to a heterozygous phenotype that is a mix of the two homozygous phenotypes. In the given scenario, we have a brown female horse with a homozygous dominant genotype (we'll use BB for brown) and a palomino male horse which is heterozygous (Bb). To determine the genotype and phenotype ratios, we can create a Punnett square.

Brown (BB) x Palomino (Bb) will produce offspring with the following genotypes: BB and Bb. Since the palomino phenotype requires a heterozygous genotype, the possible offspring can either be brown (BB or Bb) or palomino (Bb). Homozygous recessive (bb), which would result in white hair, is not possible since the brown parent provides a dominant allele (B) to all offspring. Thus, we see a phenotypic ratio of 1 brown (BB) to 1 palomino (Bb), and the genotype ratio is also 1:1 between BB and Bb.