W10 is one of the many mutations of the KIT gene that cause the Dominant White phenotype.
Dominant White 10, White spotting W10
Breeds known to carry this mutation
Quarter Horses related to the founder GQ Santana, born in 2000.
W10 causes its carriers to have a significant amount of white, ranging from a spotting pattern with extensive white on the face and legs, to the horse being completely white.
Interpretation of results
n/n: Horse does not carry the W10 mutation
W10/n: Horse carries one copy of the W10 mutation and will have a significant amount of white in its coat. It will pass the W10 mutation on to approximately half of its offspring.
W10/W10: Horse carries two copies of the W10 mutation. Please note that this is a theoretical genotype, and no horse has been identified as carrying two W10 mutations. It is suspected that embryos carrying two W10 mutations are not viable and die early in the pregnancy.
Haase et al. Seven novel KIT mutations in horses with white coat colour phenotypes. Animal Genetics 2009; 40:623-629. doi:10.1111/j.1365-2052.2009.01893.