Dogs have a wide range of coat colors, patterns, textures and lengths. Dog coat color is governed by how genes are passed from dogs to their puppies and how those genes are expressed in each dog. Dogs have about 19,000 genes in their genome but only a handful affect the physical variations in their coats. Most genes come in pairs, one being from the dog’s mother and one being from its father. Genes of interest have more than one expression (or version) of an allele. Usually only one, or a small number of alleles exist for each gene. In any one gene locus a dog will either be homozygous where the gene is made of two identical alleles (one from its mother and one its father) or heterozygous where the gene is made of two different alleles (one inherited from each parent). To understand why a dog’s coat looks the way it does based on its genes requires an understanding of a handful of genes and their alleles which affect the dog's coat. For example, to find how a black and white greyhound that seems to have wavy hair got its coat, the dominant black gene with its K and k alleles, the (white) spotting gene with its multiple alleles, and the R and r alleles of the curl gene, would be looked at. Genes associated with coat color Each hair follicle is surrounded by many melanocytes (pigment cells), which make and transfer the pigment melanin into a developing hair. Dog fur is colored by two types of melanin: eumelanin (brownish-black) and phaeomelanin (reddish-yellow). A melanocyte can be signaled to produce either color of melanin. Dog coat colors are from patterns of: Eumelanin — black, chocolate brown, grey or taupe pigment; Phaeomelanin — tan pigment, including all shades of red, gold and cream pigment; and/or Lack of melanin — white (no pigment). By 2020, more than eight genes in the canine genome have been verified to determine coat color. Each of these has at least two known alleles. Together these genes account for the variation in coat color seen in dogs. Each gene has a unique, fixed location, known as a locus, within the dog genome. Some of the loci associated with canine coat color are: Pigment shade Several loci can be grouped as affecting the shade of color: the Brown (B), Dilution (D), and Intensity (I) loci. B (brown)