Dominant White

Dominant White is sometimes alternatively called White or White Spotted/Spotting. As of right now there are 21 identified mutated versions of Dominant White and more assumed to be discovered. Currently there are only a few mutations that have tests publicly available. Dominant White horses are can be seen with a large range of phenotypes, fitting due to there being 21 different mutations! Some horses have the pigment completely inhibited, making the horse a Max White Dominant White Pinto. While others will have patterns that people are more apt to call Sabino. Dominant White horses are usually born with dark eyes, this has led to past names including the Dark Eyed Whites. Rarely Dominant White horses have blue eyes.

Dominant White Genetics

The Dominant White mutations are found at the KIT locus. Dominant White is listed as W then the number in a genetic code, W1 is Dominant White 1 for example. Many of the Dominant White mutations are dominant,  however in the case of W20, it behaves true to being incomplete dominant. It is believed that most Dominant Whites are homozygous lethal. Homozygous lethal Dominant White horses are not born, but rather they are naturally aborted early in the pregnancy. W20 is proven not to be homozygous lethal.

The Dominant White Mutations

Listed below are the current known Dominant White mutations and listed are their phenotype and what breeds that they are currently found in.

W1 is seen in Franches Montagnes. Most W1 horses are born completely white, some horses born with a little amount of colour and will whiten with age. The mutation is credited to have started with the horse Cigale born in 1957.
W2 is seen in Thoroughbreds. Many horses of W2 are completely white. The mutation is credited to have started with the horse KY Colonel born in 1946.
W3 is seen in Arabians. Many horses have slight colourization on them. The mutation is credited to have started in the horse R Khasper born in 1996.
W4 is seen in Camarillo White Horses. Horses of this line are completely white or sometimes born slight colour pigment that whitens with time. The mutation is credited to have started in the horse Sultan born in 1912.
W5 is seen in Thoroughbreds. This version ranges from completely white to Sabino like markings. The mutation is credited to have started in the horse Puchilingui born in 1984. Genetic testing is available to the public.
W6 is seen in one Thoroughbred who is almost completely white.
W7 is seen in one Thoroughbred who is almost completely white.
W8 is seen in one Icelandic who has markings more closely resembling Sabino.
W9 is seen in one completely white Holsteiner.
W10 is seen in Quarter Horses. Horses ranges from nearly all white to small white on legs. The mutation is credited to have started with the horse GQ Santana born in 2000. Genetic testing is available to the public.
W11 is seen in a German Draft horse blood line of horses that are nearly all white.
W12 was seen in a Thoroughbred colt that passed away at a young age. The mutation was possibly lethal.
W13 is seen in a Quarter Horse X Peruvian Paso cross where the horse is completely white.
W14 is seen in a Thoroughbreds ranging from completely white to mostly white. Mutation credited to Shirayukihime born in 1996.
W15 is seen in Arabians who have an expression more associated with Sabino. The mutation is credited to have started in the horse Rhevelation born in 2008.
W16 is seen in Oldenburgers who are nearly completely white. The mutation is credited to have started in the horse O’ Wie Weiss born in 2009?.
W17 is seen in Japanese Draft Horse who are completely white.
W18 is seen Swiss Warmbloods who have a more Sabino expression to them. The mutation is credited to have started in the horse Colorina Von Hoof born in ?
W19 is seen in a crossbred Arabian with approximately 50% white. The mutation is credited to have started in the horse Fanasia Vu born in 1990.
W20 is very wide spread expressing in white leg and face markings as well as white spotting on the belly. When paired with other Pinto genes, W20 enhances that amount of white on the horse. Breeds that have been found W20 positive includes: Appaloosa, Clydesdale, Franches-Montagne, German Riding Pony, German Warmblood, Gyspy Horse, Marwari, Morgan, Noriker, Old Tori, Oldenburg, Quarter Horse, Paint Horse, Paso Peruano, South German Draft, Thoroughtbred and Welsh Pony.
W21 is found in the Icelandic breed. It expresses as a patchy Sabino type phenotype.

 Check out the Dominant White album to see pictures of Dominant White Horses: