Long hair is caused by mutations in the fibroblast growth factor-5 (FGF5) gene. To date, five mutations have been identified. The longhair test identifies the p.Cys95Phe mutation, which is the most common across breeds. The shorthair allele (L) is dominant over the longhair allele (l), so two copies of the longhair allele are required to produce longhaired dogs. The specific test for the Akita breed is available: see Longhair test - Akita (DOG-LHA)
