In horses, black color (B) is dominant over chestnut color (b). Find the genotype and phenotype ratios of a cross between a hybrid black horse and a chestnut horse. What is the probability that the offspring will be chestnut color?

Phenotype: 2:2 or 1:1 / Genotype: 2:2 or 1:1 / 50% probability for chestnut color

Explanation:

If we put the two horses' genotypes in a Punnett square:

B b

b Bb bb

b Bb bb

The phenotype is describing the ending color of the offspring, where 2 of the 4 will be brown (Bb) and 2 of the 4 will be chestnut (bb), resulting in a 2:2 ratio. Genotype only refers to the alleles, where 2 of the 4 will be hybrid (Bb) and 2 of the 4 will be homozygous recessive (bb), again resulting in a 2:2 ratio. There is only a 50% chance that the offspring's phenotype will be chestnut color (bb) because the chestnut allele is recessive.