The coat of a foal depends on that of its parents, who transmit it the genes contained in their chromosomes, each horse having thirty-two pairs of chromosomes against twenty-three for humans. All coat colors derive from three basic coats: chestnut, black, and bay. They depend on the extension genes that determine whether the coat will be dark or light and agouti genes that give a plain or darker coat at the ends. It is, therefore, the horse's genotype (set of genes) that determines its physical characteristics (phenotype) through the production of pigments that color its skin and hair.