Coat Color Modifiers
A number of genes are known to affect coat color in dogs. They all interact and in some cases other, often unknown, genetic effects may also influence color and pattern.
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Hidden Patterning
K (Dominant Black) Locus
Gene: Canine Beta-Defensin 103 (CBD103)
This gene helps determine whether the dog has a black coat. Dogs with a kyky result will show a coat color pattern based on the result they have at the A (Agouti) Locus. A KBKB or KBky result means the dog is dominant black, which overrides the fur pattern that would otherwise be determined by the A (Agouti) Locus. These dogs will usually have solid black or brown coats, or if they have ee at the E (Extension) Locus then red/cream coats, regardless of their result at the A (Agouti) Locus. Dogs who test as KBky may be brindle rather than black or brown.
Did You Know?
Even if a dog is “dominant black” several other genes could still impact the dog’s fur and cause other patterns, such as white spotting.
Learn More: http://www.doggenetics.co.uk/black.htm
Citations: Candille et al 2007 -
Body Pattern
A (Agouti) Locus
Gene: Agouti Signalling Protein (ASIP)
This gene is responsible for causing different coat patterns. It only affects the fur of dogs that do not have ee at the E (Extension) Locus and do have kyky at the K (Dominant Black) Locus. It controls switching between black and red pigment in hair cells, which means that it can cause a dog to have hairs that have sections of black and sections of red/cream, or hairs with different colors on different parts of the dog’s body. Sable or Fawn dogs have a mostly or entirely red coat with some interspersed black hairs. Agouti or Wolf Sable dogs have red hairs with black tips, mostly on their head and back. Black and tan dogs are mostly black or brown with lighter patches on their cheeks, eyebrows, chest, and legs. Recessive black dogs have solid-colored black or brown coats.
Did You Know?
The ASIP gene causes interesting coat patterns in many other species of animals as well as dogs.
Learn More: http://www.doggenetics.co.uk/tan.html
Citations: Dreger and Schmutz 2011, Berryere et al 2005 -
Saddle Tan
Gene: RALY
The "Saddle Tan" pattern causes the black hairs to recede into a "saddle" shape on the back, leaving a tan face, legs, and belly, as a dog ages. The Saddle Tan pattern is characteristic of breeds like the Corgi, Beagle, and German Shepherd. Dogs that have the II genotype at this locus are more likely to be mostly black with tan points on the eyebrows, muzzle, and legs as commonly seen in the Doberman Pinscher and the Rottweiler. This gene modifies the A Locus at allele, so dogs that do not express at are not influenced by this gene.
Did You Know?
The Saddle Tan pattern is characteristic of breeds like the Corgi, Beagle, and German Shepherd.
Citations: Dreger et al 2013 -
Harlequin
Gene: PSMB
This gene, along with the M Locus, determines whether a dog will have harlequin patterning. This pattern is recognized in Great Danes and causes dogs to have a white coat with patches of darker pigment. A dog with an Hh result will be harlequin if they are also M*m or M*M* at the M Locus and are not ee at the E locus. Dogs with a result of hh will not be harlequin.
Did You Know?
While many harlequin dogs are white with black patches, some dogs have grey, sable, or brindle patches of color, depending on their genotypes at other coat color genes.
Learn More: http://www.doggenetics.co.uk/harlequin.html
Citations: Clark et al 2011 -
Merle
M (Merle) Locus
Gene: PMEL
This gene is responsible for mottled or patchy coat color in some dogs. Dogs with an M*m result are likely to appear merle or could be "non-expressing" merle, meaning that the merle pattern is very subtle or not at all evident in their coat. Dogs with an M*M* result are likely to have merle or double merle coat patterning. Dogs with an mm result are unlikely to have a merle coat pattern.
Did You Know?
Merle coat patterning is common to several dog breeds including the Australian Shepherd, Catahoula Leopard Dog, and Shetland Sheepdog.
Learn More: http://www.doggenetics.co.uk/merle.html
Citations: Clark et al 2006 -
Facial Fur Pattern
E (Extension) Locus
Gene: Melanocortin Receptor 1 (MC1R)
This gene determines whether a dog can have dark hair and can give it a black “mask” or “widow’s peak,” unless the dog has overriding coat color genetic factors. Dogs with one or two copies of Em in their result may have a mask, which is dark facial fur as seen in the German Shepherd Dog and Pug. Dogs with no Em in their result but one or two copies of the Eg, Ea, or Eh variants can instead have a "widow's peak", which is dark forehead fur.
Did You Know?
The "widow’s peak" is seen in the Afghan Hound and Borzoi, and is called either “grizzle” or “domino.”
In the absence of Em, dogs with the Eg variant can have a “widow’s peak” phenotype. In the absence of both Em and E variants, dogs with the Ea or Eh variants can express the “widow’s peak” phenotype. Additionally, a dog with any combination of two of the Eg, Ea, or Eh variants (example: EgEa) is also expected to express the grizzle phenotype.
Learn More: http://www.doggenetics.co.uk/masks.html
Citations: Anderson et al 2020, Dreger and Schmutz 2010, Schmutz et al 2003, Honkanen et al 2024, Durig N et al 2018 -
White Spotting
S (White Spotting) Locus
Gene: MITF
This gene is responsible for most of the white spotting observed in dogs. Dogs with a result of spsp will have a nearly white coat or large patches of white in their coat. Dogs with a result of Ssp will have more limited white spotting that is breed-dependent. A result of SS means that a dog likely has no white or minimal white in their coat. The S Locus does not explain all white spotting patterns in dogs and other causes are currently being researched. Some dogs may have small amounts of white on the paws, chest, face, or tail regardless of their result at this gene.
Did You Know?
Any dog can have white spotting regardless of coat color. The colored sections of the coat will reflect the dog’s other genetic coat color results.
Learn More: http://www.doggenetics.co.uk/white.htm
Citations: Karlsson et al 2007 -
Roan
R (Roan) Locus
Gene: USH2A
This gene, along with the S Locus, regulates whether a dog will have roaning. Dogs with at least one copy of R will likely have roaning on otherwise uniformly unpigmented white areas created by the S Locus. Roan may not be visible if white spotting is limited to small areas, such as the paws, chest, face, or tail. The extent of roaning varies from uniform roaning to non-uniform roaning, and patchy, non-uniform roaning may look similar to ticking. Roan does not appear in white areas created by other genes, such as a combination of the E Locus and I Locus (for example, Samoyeds). The roan pattern can appear with or without ticking.
Did You Know?
Roan, tick, and Dalmatians' spots become visible a few weeks after birth. The R Locus is probably involved in the development of Dalmatians' spots.
Learn More: http://www.doggenetics.co.uk/ticking.html
Citations: Brancalion et al 2021, Kawakami et al 2021 -
Panda White Spotting
Gene: KIT
Panda White Spotting originated in a line of German Shepherd Dogs and causes a mostly symmetrical white spotting of the head and/or body. This is a dominant variant of the KIT gene, which has a role in pigmentation.
Dogs with one copy of the I allele will exhibit this white spotting. Dogs with two copies of the I allele have never been observed, as two copies of the variant is suspected to be lethal to the developing embryo. Dogs with the NN result will not exhibit white spotting due to this variant.
Did You Know?
A de novo mutation (a genetic mutation not inherited from the parents) occurred in a female German Shepherd Dog named Lewcinka's Franka von Phenom. She was born in 2000, and all Panda Shepherds can trace their bloodline back to her.
Learn More: http://www.doggenetics.co.uk/white.htm
Citations: Wong et al 2013