One of the most obvious gross morphological differences among dogs of different breeds is the length of their hair. For the majority of registered dog breeds, the breed standard allows only one hair length. However, variable hair lengths are allowed by the standard for some breeds, such as collies, Border collies, dachshunds and St. Bernards. In other breeds, such as Pembroke Welsh Corgis, the occasional appearance of long-haired dogs (also called “fluffies” in this breed) has been a problem for breeders. It has recently been demonstrated in some dog breeds (e.g. Welsh Corgi, Collie, Border Collie, German Shepherd Dog, Miniature long-haired and Smooth Dachshund) that a missense mutation is associated with the hair-length differences among these breeds. Long-haired coat length is inherited a an autosomal recessiv trait, therefore dogs that are carriers of the long hair mutation will appear to be normal (short hair) themselves but will likely pass on the long-hair mutation 50% of the time.

Long hair is also know as Fluffy is some breeds.

The DNA test allows to distinguish between 3 possible genotypes:

1. L/L Short Hair having 2 copies of the normal short-hair allele 'L'.

2. L/l Short Hair carrying the long hair mutation - carrier having 1 copy of the normal short-hair allele 'L' and 1 copy of the long-hair mutation 'l'.

3. l/l Long Hair having 2 copies of the long-hair mutation 'l'.

Short Hair (L) is dominant over Long Hair (l)

Please note that this test Coat Length I is valid for all dog breeds, however, in the breeds listed below you should test for this mutation (Coat Length I) and for another mutation (Coat Length II) which is also responsible for Coat Length: Afghan Hound, Akita Inu, Alaskan Malamute, ChowChow, Eurasian, Husky, Prager Rattler and Samoyed