Cu Locus (Curly Coat)
Hair shape, or curl, in dogs is a complex trait that is difficult to classify, especially when comparing phenotypes across breeds. Extreme differences in phenotype are exemplified by the long, relatively straight hair of the Afghan Hound and the long, tightly curled hair of the Poodle. This locus is called Cu, and the two alleles CuC and Cu+, for straight and curly coat, respectively. The curly hair is known to be recessive. Intermediate phenotypes between these two extremes, such as the loose, spiral-shaped hair characteristic of Irish Water Spaniels, are described as kinky or wavy.
Genome-wide mapping identified association between KRT71 coding alteration and curly coat. Analysis across breeds indicates that the variant allele, KRT71151W, is uncommon in straight coated breeds, but fixed in several curly- and wavycoated breeds. Inheritence of curly coat is non-Mendelian, and the KRT71151W allele is not found in some curly-coated breeds, such as the Curly Coated Retrievers.
Some popular breeds of curly coated dogs are the Irish Water Spaniel, the Curly-Coated Retriever, the Airedale Terrier, the Kerry Blue Terrier etc.
Cadieu, E., Neff, M.W., Quignon, P., Walsh, K., Chase, K., Parker, H.G., Vonholdt, B.M., Rhue, A., Boyko, A., Byers, A., et al. (2009). Coat variation in the domestic dog is governed by variants in three genes. Science 326, 150–153.