Dog Coat Color and Type

Canine Coat Color and Type

Base Coat Color

Mammals have two pigments that are the basis of hair color: eumelanin (black) and phaeomelanin (red or yellow) (Figure 1). Whether a dog will produce eumelanin, phaeomelanin or both is determined by 3 genes:
Agouti (A locus)
MC1R (E locus) 
Dominant Black (K locus) 

Illustration of a dog with black saddle and tan coat, showing eumelanin (black) and phaeomelanin (yellow) pigments
Figure 1: Illustration of a black saddle dog displaying both types of pigment: eumelanin and phaeomelanin. 

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 (E) locus. The Agouti (ASIP) gene, also known as A locus, determines the production of Agouti Signaling Protein (ASIP), which interacts with MC1R to control phaeomelanin and eumelanin pigment switching on the hair shaft. This affects the amount, type and distribution of the two pigments in the dog’s coat. Variation at the Agouti locus can distinguish between 6 coat colors in the dog, when MC1R genotype is E/E or E/e and Dominant Black genotype is N/N. The phenotypes are listed in the order of dominance, with dominant yellow being dominant over shaded yellow and so on (Figure 2). 

A mutation resulting in a recessive variant in the MC1R gene, when homozygous (i.e., two copies denoted as e/e), causes the dog to not be able to produce eumelanin. Dogs with e/e genotypes can only produce phaeomelanin (red/yellow pigment) regardless of what their Agouti genotypes say. 

Graphic chart comparing dog coat color genotypes at Agouti and MC1R loci with illustrated phenotypes.
Figure 2: Different patterns defined by the Agouti alleles (on the left) and the phenotype observed when the dog has a homozygous recessive genotype at MC1R.

 

Coat Color Modifiers

 

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 (Figure 3). 

Infographic of showing the effect of the brown locus on each of 6 agouti patterns
Figure 3:  Illustration showing the effect of the homozygous brown genotype (b/b) on each of 6 agouti patterns. Brown modifies the eumelanin from black to brown color. The B locus does not affect phaeomelanin.

 

The dilution gene (MLPH) modifies eumelanin from black to blue and from brown to lilac (or Isabella) (Figure 4).

Graphic of four dog silhouettes showing black→blue and brown→isabella coats with genotypes
Figure 4: Illustration of the effect of the homozygous dilute genotype (d/d) on two solid dogs, one black and one brown.

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.

 

Tests Available at the VGL

Panels

Single Tests:

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