Coat Colour E-Locus (5 variants) – Dog

Coat colour in dogs is influenced by multiple interacting genes, one of which is the Extension or E-Locus, corresponding to the MC1R (melanocortin 1 receptor) gene. MC1R controls pigment production by switching between phaeomelanin (red/yellow) and eumelanin (black/brown). The normal E allele allows for dark pigment formation, while other loci like B and D can further modify the final coat colour.

Recessive e mutations (e1, e2, e3) disable MC1R, resulting in light coats—ranging from cream to red—when two copies are present. These e variants are breed-specific but functionally equivalent.

Dominant mutations at the E-Locus alter pigment distribution instead of production. The Eg (Grizzle) mutation, found in Salukis and Afghan Hounds, creates a dark-topped “Grizzle” or “Domino” pattern with a distinct widow’s peak. The Em (Melanistic Mask) mutation darkens the muzzle and face, though it can be hidden by an already dark coat.

Among all E-locus alleles, Em is most dominant, followed by Eg, while all e variants are equally recessive.