Читать книгу Horse Genetics - Ernest Bailey - Страница 74

Partial dominance, incomplete dominance, and semi-dominance are terms used interchangeably. Essentially, these terms mean the presence of just a single allele affects the phenotype and the presence of two alleles has a greater impact. A good example of this is the effect on hair color by the the dilution allele (CR) at the Cream locus (C). When a chestnut horse has one copy of the CR allele, e.g. heterozygous CR/cr, it appears as a palomino. The rich, red chestnut coat is diluted to a light cream color and the mane and tail are very pale. When a chestnut horse has two copies of the CR allele, the dilution is even greater with the horse appearing almost white. Chestnut horses homozygous for CR are called “cremellos” (Chapter 8). The effect of the variant may be additive, depending on how the phenotype is measured.