In dogs there are generally recognised colour series (loci). These are usually referred to as:
A (agouti) B (brown)
C (albino series which may not be in dogs at all) R (roaning)
D (blue dilution) E (extension)
K (dominant black or brindle) M (merle)
S (white spotting) T (ticking)
ASAP Laboratories offers coat colour tests for the A, B, D, K, E and EM Loci. The explanations below are designed to help breeders understand the background to coat colour. Please be aware that some breed standards may vary from region to region and this may also include accepted coat colours within a breed.
This locus is the major determinant of colour of hairs over the whole body unless coloured hairs are suppressed byspotting (i.e. piebald or pinto). The A locus has at least 5 alleles. These are A Y (fawn) or sable and “a” (recessive black). In combination these 2 can be used to provide information on at (tan points).
• If a dog has one copy of A Y = Fawn or Sable (with or without brindling) eg. Collie, Boxer and Great Dane
• If a dog is a = Black. eg. typical Labrador Retriever
• If a dog is at at or at a = Tan points (with or without brindling) eg. Typical Rottweiller and Doberman, also known amongst breeders as black and
tan. There can be some confusion when the tan is diluted to a pale silver colour and the dog can appear to be black and white.
• If a dog is aw = Wild-type agouti (cream to red hair with black tips)
• If a dog is As = Saddling
This locus is named the agouti locus and it produces much of its effects by controlling the distribution of pigments within individual hairs. The various alleles (genes) in the agouti series act differently on hairs in different parts of the body. The classic agouti hair has multiple bands of contrasting colour which mark alternating episodes during the growth of the hair when the production of black pigment was allowed and then inhibited. The multi-banded agouti guard hair is distinctive from the dark tipped sabled hair in which black pigment was deposited during the initial stages of hair growth but then inhibited for the balance of the growth of that hair.
“a” locus red -the body colour of a typical Belgian Malinois or a Red Border Collie -also referred to as dominant yellow or
B (brown) locus
Commonly called liver dilute, red dilute or brown dilute -black pigment is lightened and reddened to chocolate, liver or deep red. The alleles at the B locus are related to the production of tyrosinase related protein 1 (TYRP1) and determine the degree to which an animal expresses tyrosinase, a brown-black protein related to the production of melanin, in its coat and skin (including the nose and paw pads).
Results are reported as:
Bb: Carrier of Brown
bb: Brown Coat and Nose
B is dominant to b. An animal that is has at least one copy of the B allele will have a black nose, paw pads and eye rims while
an animal that is homozygous for any of the b alleles will have a liver nose, paw pads and eye rims.
Red pigments are lightened from red to tan. Liver Dobermans, Pharaoh Hounds and Ibizan Hounds are common examples.
D (dilute) locus
The D locus can alter the intensity (dilution) of pigment. Animals which are “dd” exhibit grey or blue fur instead of black, and light tan or “Isabella” instead of brown. This tan is similar to some AY shades but lacking any banding or black tips on individual hairs.
The alleles at the D locus (the melanophilin gene or MLPH) are related to the dilution of eumelanin and/or phaeomelanin and
determine the intensity of pigmentation.
There are two known alleles:
D = Not Diluted
d = Diluted (Black becomes grey or blue; brown becomes light tan or “Isabella”)
So results are reported as:
DD: Full Color
Dd: Dilute Carrier
D is dominant to d. Homozygosity of d is sometimes accompanied by hair loss and recurrent skin infl ammation, a condition
referred to as either colour dilution alopecia (CDA) or black hair follicular dysplasia (BHFD) depending upon the breed of dog.
The MC1R gene, or E Locus is responsible for the black masks when E and is also the locus responsible for most shades of yellow and red. There are three possible forms Black (E), melanistic mask (EM), and Yellow (ee). The E-Allele test determines how many copies of the recessive “e” alleles a dog carries. The EM-Allele test determines how many copies of the melanistic mask allele a dog carries. This test can be used for individuals with black dogs to determine whether there is a mask.
Results are reported as:
Ee: Carrier of Red to Yellow
ee: Red to Yellow
The K locus plays a key role in coat color. This locus is fairly new in our understanding of canine colour, and includes traits formerly attributed by some to other genes.
The first allele, which is dominant, is KB or dominant black. The KB allele is actually a mutation that does not allow the agouti gene to be expressed. Because this mutation is dominant, a dog only needs to have one copy of the mutation to suppress the agouti locus. A dog that has one or two copies of the Dominant Black allele will only express his base coat colour, which is determined by the B-Locus and E-Locus. He will not express any colours that occur from the agouti gene, such as “black and tan” or “tricolour.”
Any dog with at least one KB allele will be self-coloured so KBKB, KBKbr, KBKy will all be self-coloured ie. Solid colour in
The second allele is known as the “brindling” allele, and is represented as Kbr. The Kbr allele is a separate mutation that still allows the agouti gene to be expressed, however, causes brindling of the agouti patterns. The agouti gene represents several different colours, such as fawn/sable, tricolour, tan points, or recessive black. The Kbr allele is recessive to the KB allele; however, it is dominant over a third allele, Ky.
Therefore, for a dog to express the brindle pattern, he must be either Kbr Kbr or Kbr Ky. Dogs that are KB Kbr will not appear brindle, but can still pass on that allele and potentially produce brindle offspring.
The third allele is represented as Ky. This allele allows the agouti gene to be expressed without brindling. When a dog is Ky Ky at the K-locus, the agouti locus determines the dog’s coat colour.