D-Locus (Dilute Coat Color)
The MLPH gene codes for a protein called melanophilin, which is responsible for transporting and fixing melanin-containing cells. A mutation in this gene leads to improper distribution of these cells, causing a diluted coat color. This mutation is recessive, so two copies of the mutated gene (AKA the D allele or the D locus) are needed to produce the diluted coat color.
This mutation affects both eumelanin and phaeomelanin pigments. These pigments control the color of the dog. Black, brown, and yellow dogs are all affected by the D locus. However, the effects of the dilution are more pronounced in black dogs. A diluted black dog becomes known as a blue dog. Names for this color trait vary across the different breeds, with charcoal, slate, or grey being common names. A diluted chocolate dog is often referred to as having a lilac coloration and a diluted yellow dog is known as having a champagne color. All the dogs that express the diluted colorations have a d/d genotype. They are also coded as B/B or B/b, b/b, and e/e respectively, with regards to the E and B loci, which determine coat color.
Because the mutation responsible for the dilution phenotype is recessive, a dog can be a carrier of the dilution gene and still appear to have a normal coat color. These dogs can pass on either the full-colored genes or the diluted trait's alleles to any offspring. This means that two dogs that appear full-colored can have a diluted puppy. This makes DNA testing for the D locus an important breeding tool, whether breeding for a dilute coat, or to avoid it.
|Chocolate||Dilute||Basic Color Description|
|B/B or B/b||D/D||Black|
|B/B or B/b||d/d||Blue|
D Locus Testing:
Animal Genetics currently offers a test for the D-Locus to determine how many copies of the recessive allele a dog carries.
Dogs can be DNA tested at ANY age.
Animal Genetics accepts buccal swab, blood, and dewclaw samples for testing. Sample collection kits are available and can be ordered at Canine Test Now.
Testing Is Relevant for the Following Breeds:
Animal Genetics offers DNA testing for dominant D allele. The genetic test verifies the presence of the mutation and presents results as one of the following:
|D/D||Non-dilute||The dog carries two copies of the dominant "D" allele. The dog will express a normal, non-dilute coat color and will always pass on a copy of the "D" allele to all offspring.|
|D/d||Carrier of dilute||Both the dominant and recessive alleles detected. The dog will have a normal, non-dilute coat and is a carrier of the dilute coat color. The dog can pass either allele on to any offspring.|
|d/d||Dilute||The dog has two copies of the recessive "d" allele and will have a dilute colored coat. He will always pass on a copy of the dilute allele on to any offspring.|