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Our stud and dams genetics

D Locus (MLPH)

Dark areas of hair and skin are not lightened (DD)

The D locus result that we report is determined by three different genetic variants that can work together to cause diluted pigmentation. These are the common d allele, also known as “d1”, and the less common alleles known as “d2” and “d3”. Dogs with two d alleles, regardless of which variant, will have all black pigment lightened (“diluted”) to gray, or brown pigment lightened to lighter brown in their hair, skin, and sometimes eyes. There are many breed-specific names for these dilute colors, such as “blue”, “charcoal”, “fawn”, “gray”, and “Isabella”. Note that in certain breeds, dilute dogs have a higher incidence of Color Dilution Alopecia. Dogs with one d allele will not be dilute, but can pass the d allele on to their puppies.

What is the fading gene?

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The "fading gene" in dogs is often referred to in discussions about coat color, particularly in relation to puppies that are born with a certain color that fades or changes as they mature. This phenomenon is not due to a single gene, but rather to a combination of genetic factors that influence coat color and how it can change over time. One of the most well-known examples involves the genes responsible for the "blue" coat color in dogs, which can fade to a lighter gray as the dog ages.

The most scientifically understood mechanisms behind color fading or changes in dogs involve the genetics of coat color dilution and progression. These are controlled by various genes, including:

  • The D Locus (Dilute Locus): This gene affects the intensity of the coat color, turning black into blue (a dilute form of black) or red into cream. Dogs with the dilute gene (dd) will have a faded version of their primary coat color.

  • The Merle Gene: The merle pattern causes a mottling effect that can lighten the base coat color, leading to patches of diluted pigment and patches of full pigment. This gene can cause a significant variation in the appearance of the coat over time, especially if the dog is also affected by other coat color genes.

  • The G Locus (Greying Gene): This gene causes dogs to be born with a darker coat that gradually lightens or grays as they age. This is commonly seen in breeds like the Bedlington Terrier and the Poodle.

  • Progressive Graying: This is not linked to a single gene but is a trait observed in some breeds where the coat color fades or grays progressively with age, regardless of the original color. This is seen in breeds such as the Portuguese Water Dog and the Bearded Collie.

 

Genetic testing can predict the likelihood of color changes in puppies as they mature, depending on the breed and the specific genes involved. Breeders and geneticists use knowledge of these genes to predict and describe the coat colors of puppies in a litter, including any potential changes as they grow.

Genetic testing of the MFSD12 gene will reliably determine the number of copies of the intensity gene Mutation that a dog carries. Phaeomelanin dilution associated with mutations of the MSFD12 gene is known to be inherited in an Autosomal Recessive manner in dogs. Carrier dogs (I/i) do not display an extreme phaeomelanin dilution, but when bred with another dog that also is a carrier (I/i), there is a 25% chance of having pups with light cream or white coat color (if also e/e at the E Locus). Reliable genetic testing is important for determining breeding practices. Dogs that are not carriers of an i mutation have no increased chance of having pups with a light cream or white coat color.

The I Locus (Intensity) corresponds to the MFSD12 gene that is important in determining the shade of the light pigment (phaeomelanin) in dogs. Mutations in this gene modify the expression of the phaeomelanin (reds, yellows and creams) in the hair resulting in an extreme lightening of the coat color of dogs. Canine coat color determination is complex due to interactions of multiple genes responsible for both color and anatomic placement of the color. A dog with two mutant copies of the MFSD12 gene will have an extremely light phaeomelanin that will cause a dog that is e/e at the E locus to have a coat color that is light cream or white.

Dogs with I/I and I/i genotypes typically have an unmodified (yellow to red) phaeomelanin pigment. Dogs with an i/i genotype typically have a less intense, cream or white phaeomelanin pigment. However, there are other, unknown genes that influence the final shade of phaeomelanin; genes responsible for the red shade of phaeomelanin are still unknown. Dogs that carry at least one copy of the i Allele can produce light cream or white dogs if bred to another dog that is also light cream or white (i/i) or a Carrier of light cream or white (I/i). The color of the dog’s nose and footpads is still dependent on the B locus; there is no evidence that the I Locus impacts the nose and footpad color.

The I Locus (Intensity) coat color test evaluates the MFSD12 gene to determine the I locus genotype for the dog. This Mutation has been associated with the extreme dilution of the light, yellow to red pigment (i.e., phaeomelanin) in many breeds, associated with an e/e genotype at the E locus. The phaeomelanin pigment can also be seen in dogs with a dark coat color that express their A locus (Agouti) genotype; for example, a dog with tan (phaeomelanin) points (ky/ky and at/at) or the light base color of hairs on sable/fawn (ky/ky and Ay/-) dogs.

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