Base coat colours
Coat colour dilutions
Genetic disorder tests
W20 is a version of the KIT gene that is thought to cause relatively subtle white markings such as a blaze and socks - and sometimes even less white. It has a white-increasing effect when it is inherited in combination with other white marking genes (article abstract here). Our understanding of what to expect from W20 will increase as we do more testing.
W20 has been found in a very wide range of horse breeds. The following are just some of the horse and pony breeds where some individuals have tested positive to W20: Thoroughbreds, Welsh Ponies, Quarter Horses, Appaloosas, Warmbloods, Gypsy Vanner, Noriker, Miniature Horses... the list goes on.
If your horse has a blaze and one or more socks, or perhaps a few white belly spots that have not been explained by other white marking genes, test for W20 as well as sabino 1.
Fred, a Warmblood, is homozygous for W20. He has four socks, a blaze, a belly splash and birdcatcher spots.