THE PALETTE OF COLOR AND PATTERN - GENETIC LOCI

 

Color and pattern are produced by many loci interacting. The alleles within the locus are listed from most dominant to least dominant. Colors and patterns that are disqualified by the breed standard are highlighted in red. The older genetic model by Little has been found to have a few errors. These lists of alleles follow the current research of Dr. Greg Barsh at Stanford University, and research at VetGen.

A Locus - How Pigment is Distributed On the Dog's Hair Shaft and Body

A - Once thought to be Dominant black - the body is self colored with no banding (Labradors, Aussies). Now most geneticists believe blacK is at the K locus.

a^y - Sable - The hair shaft is light with black or liver tipping or black hairs interspersed (Rough collie, Border collie, Shetland sheepdog).

a^s - Saddleback pattern - A saddle of pigment on a tan dog (German shepherd, Airedale, rare in Aussies).

a^t - Tan point pattern -The dog has tan pigment or "points" on the legs, muzzle, eye spots, under the tail, and the front of the shoulder (Dobe, Rottie, Aussie).

a - Recessive black (German shepherds, Shelties, possibly some Aussies)

 

B Locus - Pigment Color

B - Black

b - red (also called liver or chocolate). There are at least 3 mutations of b. They may or may not be responsible in part for the vastly different shades of red.

 

C Locus - Pigment Development

C - Normal pigment development

c^ch - Chinchilla allele - Reduces red and yellow pigment, black unaffected ("White" tiger, some terriers, white GSDs with dark eyes and nose)

c^a - Albino (Complete lack of pigment in skin and eyes-rare in dogs in general)

 

D Locus - Dilution of pigment

D - Normal pigment intensity - black or red

d - Pigment is uniformly diluted so that black becomes uniform blue (Dobes) and liver becomes isabella (Weimaraners) Also called "Maltese Dilution". Does not affect tan points. This is one of the most common mismarks in Aussies.

 

E Locus - Pigment Restriction/Extension, a very diverse set of alleles

E - Full extension of pigment throughout the hair shaft (Most Aussies are EE).

E^M- Hyperextension mask - black or liver mask on muzzle, displacing tan points on muzzle if they're present (Aussie, German shepherd, Dane, Pug, Dogue de Bordeaux). In merles the mask can be merle or solid depending on how the merle pattern falls.

e - Restriction of black and liver pigment in coat, normal intensity nose leather and eye rims. (Yellow Lab, Golden retriever, Irish setter) Another common mismark in Aussies, sometimes called "Palomino or blond" Aussie.

 

H Locus - Harlequin modifier - This gene acts upon merle but remains unseen in non merles

H - Harlequin (Sometimes called "tweed" in Aussies) - causes different degrees of lightness in merled areas. Some specimens have 4 or more distinctly different shades of blue and gray evenly distributed. In Danes H is known to be lethal in homozygotes - the HH embryo dies early in development. It is not known whether the form of H that occurs in Aussies is lethal in homozygotes. This gene's allowability in Aussies is controversial and somewhat dependent on whether it produces any white lacy areas on the individual being judged. (Danes, Aussies). It is also not certain whether Harlequin and Tweed are the same gene or allelic to each other.

h- No modification of normal merle pattern (Aussies, Rough & smooth collies, Dachshunds)

 

K Locus - Suppresses the presence of tan point pattern when present as the dominant. Once mistakenly categorized in the A series as dominant blacK.

K - Self color - Covers up action of genes at A locus

k^br - Allows A series to be expressed with brindling in tan areas or all over brindle.  A dog that is (Kk^br) would be black and not express the brindling regardless of what was at the A locus. (a^y- k^br-) is a whole body brindle.  A dog that is  (a^t- k^br-) has brindle restricted to the tan points.

k - Like a clear window allowing genes at the A locus to be expressed.

 

M Locus - Merle (A pattern of pigment reduction in the eyes and skin)

M - Merle (In a single dose, M produces patches of blue on a black dog or champagne on a liver dog. In a double dose, much of the body's pigment is lost and often the hearing as well - Aussies, collies, Border collies, Shelties, Dachshunds)

m- Non merled or "normal" allele (No merle pattern - Aussies, collies, Border collies, all breeds in which merling does not occur)

 

S Locus - Various patterns of white spotting

S - Solid color (No white spotting pattern - Labs, self colored Aussies, Dobes, Irish setters)

sⁱ- Irish spotting pattern (Typical "Lassie" markings - Rough collies, most Aussies, Shelties)

s^p- Piebald spotting pattern (Non symmetrical random white areas - Beagles, Foxhounds, Caanan dog, some Aussies) Also called "Pattern white" in Aussies.

s^w - Extreme white spotting pattern (Most or all of the dog is white - Pyrenes, Samoyed, Kuvaz, few Aussies). Color headed white may be caused by modifying genes acting on this extreme white gene.

NOTE: Some of these alleles at the S locus may have incomplete or codominance. A dog that is (sⁱ s^p) may show both patterns simultaneously, for example.

 

T Locus - Ticking (Spots or flecks of color in white areas where the dog's actual color shows through smudges on the white areas. On the upper leg ticking might be black, blue merle, red, red merle, while on the lower leg the tick marks will be tan if the tan point pattern is present.

T - Ticking (Dalmations, Border collies, Aussies)

t - No ticking (White areas are plain white - Collies, Aussies, Foxhounds)

 

 

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