Coat color genetics part III: A-locus (Agouti)

by Annika Farstad
© 2006

The A-locus is a pattern locus. It allows for the distribution of pigment.

There are several allels at the A-locus, these influence the relative amounts and location of red and black pigment in both the individual hairs, and in the coat as a whole.
The most important agouti allels for Chinese Crested, in order of dominance;


(a^y) Sable:
Some solid black hairs intermingled amongst reddish hairs (cream to yellow to red)


(a^w) Wild Agouti:
Produces the Wolf color, where dark and light colours alternate down the length of the coat hairs.


(a^t) Black & Tan:
This produces a tan-point pattern, which means the dog will be black with areas of tan pigment on the sides of the muzzle, throat, belly, inside the ears, on the chest, over each eye, on all four feet and part of the legs, around the anus and the underside of the tail.
The extent and area of the tan varies and may show in either just one or two of these points or all of them, or could extend beyond them. The depth of pigment also varies and may be as a deep rich tan colour or a very pale cream.
When modified by the gene for white (see the spotting (S) locus) it will produce a tri-colour.

It is suggested that there might be a separate allel
(a^s) Saddle, or alternatively that this might be a variation on Black & Tan : Dark saddle with extensive tan markings on head and legs. Dogs with saddles are often born nearly all black, and the colors continue to come in for the first few years of their life. Individual black hairs are all black, but graying throughout the coat, especially the neck area, can also appear.


a (Recessive Black)

(a^y) Sable: (also called a^y-red, agouti-red, non-solid red or dominant red/yellow). Sable colour is a red background and often has black overlay and/or black hairs intermingled amongst hairs of reddish color. When sable Cresteds are born the black overlay can make them look very dark, in some cases they look black because they are so dark. With age the black hairs fade leaving the red, which often lightens so you end up with dogs of various shades from pale sand to a deep rich red. The shade depends upon how other genes interact with this one. Sable dogs may develop greater or lesser extent of Dark tipping and/or intermixture of Dark hairs with growth of the mature coat. In some breeds sable is also further divided according to fenotype; - Red Sable; A sable dog with intense red in the areas without black hairs. - Cream Sable, often used to describe sables in which all the red is faded to cream/sand. - Grey sable (or silver sable or grey) - Black sables are much darker than the averge sable An example of color changes in a sable dogs from puppy to adult can be seen in the pictures below;