Mammals have two pigments that are the basis of hair color: eumelanin (black) and phaeomelanin (red or yellow). One of the genes involved in the production of these pigments in many species including dogs is Melanocortin 1 Receptor (MC1R) which is also known as the Extension locus. Other genes modify how much eumelanin and phaeomelanin are produced and this results in the variety of colors and patterns found in the domestic dog. For example, the Brown gene, Tyrosinase-Related Protein 1 (TYRP1), is a modifier that dilutes black pigment to brown but does not affect red pigment. While Agouti (ASIP) organizes the distribution of black and red pigments. Beta-defensin (CBD-103), which so far has been found to be unique to dogs, is responsible for dominant black (K locus). The dilution gene (MLPH) dilutes both black and red pigments. Additional genes have been shown to also dilute the coat and add white patterns some of which are specific to certain breeds. As new discoveries are made we will update our information and educational resources. Below are the current genetic tests offered by the Veterinary Genetics Laboratory for dog coat color.