The L Locus (Long Hair/Fluffy) Lh1 trait test evaluates the L Locus for the common Lh1 Mutation that has been associated with long hair in many breeds including various Retriever, Corgi, and Dachshund breeds, among others. Long hair is also referred to as fluffy coat in some breeds. This test will reliably determine if a dog has one of the following genotypes at the L locus:
This dog carries two copies of Sh which results in short hair. This dog will pass on Sh to 100% of its offspring.
Interpretation: Shorthaired (does not carry long hair)
This dog carries one copy of the Sh and one copy of the Lh1 mutation which results in short hair. This dog will pass one copy of Sh to 50% of its offspring and one copy of Lh1 to 50% of its offspring. This dog can produce Lh/Lh offspring if bred to a dog that is also a Carrier of an Lh mutation (Sh/Lh or Lh/Lh).
Interpretation: Shorthaired (carries one copy of long hair)
This dog carries two copies of Lh1 which results in long hair. This dog will pass one copy of Lh1 to 100% of its offspring.
Interpretation: Longhaired (carries two copies of long hair)
The L Locus impacts canine hair length as a result of a DNA variant in the FGF5 gene that prevents FGF5 from functioning as a hair growth termination signal in the hair follicle.
Genetic testing of the FGF5 gene will reliably determine whether a dog is a genetic Carrier of long hair. Long hair is inherited in an Autosomal Recessive fashion, meaning that two copies of the Lh variant are required to produce long hair. Dogs with two copies of the Lh variant of FGF5, therefore, have long hair due to the lack of the hair growth termination signal. Dogs with one copy of Lh or no copies of Lh will have short hair. However, this dog’s coat type is also dependent on the dog’s genotypes at many other genes.
NOTE: Other mutations in the FGF5 gene are known to cause longhair in dogs. Some mutations are found across many breeds (like the common Lh1 Mutation) and others are found primarily in specific breeds (such as Lh2 in the Akita, Eurasier, Samoyed, and Siberian Husky and Lh4 in the Afghan Hound, Eurasier, and French Bulldog). Testing for the common Lh1 variant is sufficient for many breeds such as various Retriever, Corgi, and Dachshund breeds, among others. However, some breeds may carry other longhair mutations in their population and may benefit from testing for other specific longhair mutations because dogs with two different mutations present on different copies of the FGF5 gene may have long/fluffy hair.
There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.
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Housley DJ, Venta PJ. The long and short of it: evidence that FGF5 is a major determinant of canine ‘hair’-itability. Anim Genet. 2006 Aug; 37(4):309-15.