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 an different mutation has been found that influences hair length in all long-haired cat breeds. The Hair Length Norwegian Forest test (K462) tests for the Norwegian Forest cat specific mutation in the FGF5-gene and has two variants (alleles). The recessive allele results in long hair and the dominant allele results in short hair.
The Hair Length Norwegian Forest test encloses the following results:
| Result Hair Length Norwegian Forest test | Hair Length |
|---|---|
| M2/M2 | Long Hair, unless modified by another mutation influencing hair length |
| N/M2 | Short Hair, unless modified by another mutation influencing hair length |
| N/N | Short Hair, unless modified by another mutation influencing hair length |
