The Fibroblast Growth Factor 5 (FGF5) determines the hair length. Four mutations in FGF5 have been identified that influence hair length in different breeds. There are breed specific mutations for Ragdolls, Norwegian Forest Cats and Main Coons and a different mutation has been found that influences hair length in all long-haired cat breeds. In the table below the possible combinations of these mutations are indicated.

Ragdoll mutation Norwegian Forest mutation Maine Coon mutation all breeds mutation FGF5 Gene Hair Length
N/N N/N N/N N/N N/N Short
N/M1 N/N N/N N/N N/M1 Short
N/N N/M2 N/N N/N N/M2 Short
N/N N/N N/M3 N/N N/M3 Short
N/N N/N N/N N/M4 N/M4 Short
M1/M1 N/N N/N N/N M1/M1 Long
N/M1 N/M2 N/N N/N M1/M2 Long
N/M1 N/N N/M3 N/N M1/M3 Long
N/M1 N/N N/N N/M4 M1/M4 Long
N/N M2/M2 N/N N/N M2/M2 Long
N/N N/M2 N/M3 N/N M2/M3 Long
N/N N/M2 N/N N/M4 M2/M4 Long
N/N N/N M3/M3 N/N M3/M3 Long
N/N N/N N/M3 N/M4 M3/M4 Long
N/N N/N N/N M4/M4 M4/M4 Long