The G Locus

This webpage is part of a series on Dog Coat Color Genetics and was last updated on November 8, 2008 by Sheila Schmutz

Little (1957) described graying as a progressive change resulting in a lightening of the hair coat as the dog ages. He suggested that this could be a dilution gene but it is not like the Weimaraner dilution gene, which causes pups to be born a diluted color and remain so. The gene that causes this in dogs, has not yet been discovered. Little (1957) reported that the G allele associated with greying is dominant.

Progressive Graying

This Standard Poodle demonstrates the effects of this gene in a very dramatic way. The small black spot by her neck is the result of a rabies vaccination! It will take a long time for that black hair to change to silver. Show dogs that have this coat color should be vaccinated in a less obvious place.

Progressive graying also occurs in the Cairn Terrier, Bedlington Terrier, Havanese, Briard, Puli, Old English Sheepdog, Bearded Collie, Bouvier des Flanders and other breeds.

Jester, the Kerry Blue Terrier at the right, illustrates that the muzzle of dogs with a EM allele will not not lighten by the same age as the rest of their body. Not all Kerry Blue Terrier lighten to the same extent.

Linda Hall took the photos of some of her grey Puli over the years and has shared them. The photo above illustrates that Puli have "progressive greying". These dogs were all born black. She refers to them as "graying", "silver" and "black". Not all the Puli continue to go to the pale silver color. Some stay a darker grey.

Geriatric Graying

Many dogs grey in advanced age. However most don't grey over all of their body. Contrary to progressive greying, geriatric greying is most noticable on the face. Egret, a Large Munsterlander, already had a white muzzle when young but the white around her eyes began about 10 or 11. The dark spot in her eye is another pigmentation change that can occur with age.

The Labrador Retriever at the right has greyed mostly around the muzzle.

Progressive graying also occurs in horses and that trait was recently mapped to horse chromosome 25, considered the equivalent of human 9q. The gene has not yet been found.

  • Locke, M.M. et al. 2002. Linkage of the grey coat colour locus to microsatellites on horse chromosome 25. Animal Genetics 33:329-337
  • Swinburne J. E. et al. 2002. Assignment of the horse grey coat colour to ECA25 using whole genome scanning. Animal Genetics 33:338-342
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