The A locus is responsible for a number of common coat patterns in the dog. Expression of all of them requires any combination of two Ky or Kbr alleles at the K locus, and at least one E or EM allele at the E locus. The gene involved is the Agouti gene, and variations in it are responsible for fawn and sable dogs (A^y), wild type (a^w), tan points (a^t), and recessive black(a).

analysis proves absence or presence of the mutation typically responsible for fawn or sable. In fawn/ sable dogs this test shows if other agouti alleles are present but hidden (only one copy of A^y). It also demonstrates how many copies of this allele are hidden in dogs, which cannot express agouti types (K^BK^B,  K^B  k^br, K^B k^y, at the k locus and/or ee at the E locus).

shows whether a black dog is black due to “recessive black,” or the more common black at the K locus. It also reveals whether a non-black animal carries “recessive black.” (e.g. German Shepherd Dog, Shetland Sheepdog)

This test is for the 'bd', 'bc' and 'bs'variants, which are described in all dog breeds and are responsible for the brown coat colour, which is also known in some breeds as liver, chocolate, chestnut, sedge, and less frequently, red. Two copies of the b-allele are needed to dilute black pigment to brown. For red or yellow dogs, the brown allele does not dilute the hair colour, but will change the colour of nose and foot pads from black to brown if two brown alleles are present.

When one of the variants is found homozygous (bd/bd, bc/bc or bs/bs), dark pigment (eumelanin) is diluted to brown in the pigmented areas. However, when several variants of the B-locus are found in heterozygous state (example N/bd and N/bc), it is not always possible to directly determine the influence on the eumelanin because this depends on whether the variants are located on the same or different chromosmes, however, the dog will definitely pass the variants to its offspring.

Australian Shepherd and Lancashire Heeler

French Bulldog

The D locus is the primary locus associated with diluted pigment, which results in coats that would otherwise be black or brown instead showing up as gray, or blue in the case of black, and pale brown or Isabella in the case of brown. The melanophilin gene has recently been shown to be responsible, but not all of the dilute causing mutations have been identified yet.

A recessive mutation in the melanophilin gene was identified as the cause of colour dilution phenotypes in the dog. Two alleles (variants) are described: the dominant full colour (D) and the recessive dilute (d). Two copies of dilute are needed to lighten black pigment to grey (often called blue) and red pigment to cream (also called buff). A diagnostic DNA test identifies the specific variants of the MLPH gene.

Please note that in the Chow Chow, Thai Ridgeback and Sloughi breeds, there is another mutation that can cause coat colour dilution, it is the D2 Locus mutation and in those breeds both D1 Locus and D2 Locus mutations must be tested for complete analysis.

Please note that in the Chihuahua, Italian Greyhound and Hungarian Pumi breeds, there is another mutation that can cause coat colour dilution, it is the D3 Locus mutation and in those breeds both D 1Locus and D3 Locus mutations must be tested for complete analysis.

Coat Colours

As with other mammals, dogs have two major types of pigment in their coat: dark pigment (Eumelanin) which is responsible for black and brown in the pigmented areas, and yellow pigment (Phaeomelanin) which is responsible for red, yellow, orange, golden, cream, apricot in the pigmented areas. The colour varieties seen in dogs are due to genes controlling the amount, extent, and distribution of these two colour pigments.

E-Locus

The 'e1' variant

Australian Cattle Dog

E-Locus Special colours: 'eA', 'eG' and 'eH'

EM-Locus Melanistic Mask

Order of dominance: EM> EG> E> EH> e.

The K locus plays a pivotal role in coat colour. This locus is a relative newcomer in our understanding of canine colour, and includes traits formerly attributed by some to other genes.

The dominant allele in the series is K^B, which is responsible for self-colouring, or solid coloured fur in pigmented areas. This trait was formerly attributed to the Agouti (A) locus as A^S, but recent breeding studies had shown this not to be the case.

There are two other alleles, k^br, and k^y. K^B is dominant to both k^br and k^y, while k^br is dominant only to k^y. k^br is responsible for the brindle. The recessive allele, k^y, allows the basic patterns of the A locus to be expressed. So too does the k^br allele, but with brindling of any tan, fawn, or tawny areas. Any animal with at least one K^B allele will be self-coloured.

Any animal with at least one k^br allele, and no K^B alleles will be brindled on agouti background (see A locus). Any animal with two k^y alleles will show agouti patterns (see A locus). and k^y

LABOKLIN can presently test for these two alleles. In some breeds, where no brindle is present, this represents a complete analysis of the locus. An example would be the Pug. In breeds where the breed standard disqualifies all but self-colored dogs, testing for these two alleles is once again all that is needed. Any animal with two K^B alleles cannot produce anything except self-coloured offspring. A prime example here is the Labrador retriever. In breeds where many variations are allowed, these tests can help predict the probability of potential litters to include fawn, sable, tawny, tan point, tricolor or recessive black puppies.

I-Locus controls the intensity of the red pigment (phaeomelanin). Phaeomelanin is the tan pigment including all shades of red, gold, fawn, sable and cream pigments. The richness of the red colour varies in the different breeds and within a breed, from the very rich red of the Irish setter to cream. This intensity is controlled by the I-Locus which has recently been identified.The dominant I-allele stands for intense phaeomelanin (red, orange, yellow), the recessive i-allele is responsible for for cream, cream-white or white.

The expression of the phaeomelanin on the dog body, is initially determined by the loci E, K and A locus. The I-Locus decides how bright or rich the red colour is.

A test is now available at Laboklin.