Component name Genome Accession(s) Component representation Proteins; Chromosome 1: CM000001 . When livestock were domesticated about 7,000 to 9,000 years ago, dogs served as herders and guardians of sheep, goats, and cattle. Melanocytes are the cells within the hair follicles that add melanin to the hair as it grows and determine basic coat color. The loci associated with coat color in dogs are: A (agouti) locus. Characteristics of loyalty, friendship, protectiveness, and affection have earned dogs an important position in Western society, and in the United States and Europe the care and feeding of dogs has become a multibillion-dollar business.  There are two known alleles that occur at the W locus: W is dominant to w, but the dominance of W > w is incomplete. Wijesena, H.R.  The H locus is a modifier locus (of the M locus) and the alleles at the H locus will determine if an animal expresses a harlequin vs merle pattern.  There are two known alleles that occur at the L locus: L is dominant to l. A long coat is demonstrated when a dog has pair of recessive l alleles at this locus. Research suggests that hairlessness is caused by a dominant allele of the forkhead box transcription factor (FOXI3) gene, which is homozygous lethal. Research indicates that the majority of variation in coat growth pattern, length and curl can be attributed to mutations in four genes, the R-spondin-2 gene or RSPO2, the fibroblast growth factor-5 gene or FGF5, the keratin-71 gene or KRT71 and the melanocortin 5 receptor gene (MC5R). Get exclusive access to content from our 1768 First Edition with your subscription. Defective MLPH prevents normal pigment distribution, resulting in a paler colored coat.. Many … For example, you may see a colored dog with white markings. , In 2014, a study found that a simple repeat polymorphism in the MITF-M Promoter is a key regulator of white spotting and that white color had been selected for by humans.. Genotypes of dogs of these 3 breeds are usually L/L or L/l, which does not match with their long-haired phenotype. But recently the research group of Tosso Leeb has identified additional alleles in other breeds. Many genes impact the color of a dog by manipulating these two basic pigments. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. In fact, each species of plants and animals has a set number of chromosomes. Dogs are even used in therapy in nursing homes and hospitals to encourage patients toward recovery.