The Fibroblast Growth Factor 5 (FGF5) determines the hair length. The Hair Length test (H765) tests for the genetic status of the FGF5-gene and has two variants (alleles). The allele S is dominant and results in short hair. Only when the dog has two copies of the recessive allele L the dog has long hair. Some breeds, such as Labradors, are fixed for the dominant allele S. Other breeds, such as Poodles, are fixed for the recessive allele L and some breeds, such as Dachshund, can have either long or short hair. In some breeds another, yet unidentified, mutation is present that influences hair length. This unidentified mutation is known to occur in Afghan Hounds, Yorkshire Terriers, and Silky Terriers.

The Hair Length test encloses the following results:

Result Hair Length test

Hair Length

L/L

Long Hair, unless modified by another mutation influencing hair length

S/L

Short Hair, unless modified by another mutation influencing hair length

S/S

Short Hair, unless modified by another mutation influencing hair length

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