Smooth hair: S (dominant)
Curly hair: s (recessive)
Black hair: B (dominant)
Chestnut hair: b (recessive)
In horses, hair texture and color are determined by specific alleles. Smooth hair is denoted by the dominant allele S, while curly hair is represented by the recessive allele s. Similarly, black hair is determined by the dominant allele B, whereas chestnut hair is associated with the recessive allele b.
The combination of these alleles results in the observable traits of the horse's coat. Smooth and black-haired horses can have genotypes SSBB, SSBb, SsBB, or SsBb, while curly and chestnut-haired horses have the genotype ssbb. The dominance and recessiveness of these alleles contribute to the genetic diversity and variation in the coat characteristics of horses.