Canine Coat Color with an emphasis on Colors in Borzoi

©1995,1996, 1997 Bonnie Dalzell, MA, version 8-21-97

About this article. This is a work in progress. As of 8-21-97 links are being added to pictures with examples of the colors in question.

Is the web location of the latest version of this article. Many writers have written books that discussed canine coat color genetics. The best known of these books is by Little; the most recent that I have read is by Malcolm Willis. Because canine coat color genetics is an area of knowledge that is only partially understood NONE of the published accounts has proposed a completely correct genetic system for dog coat colors.

It is also most important to understand that there is a major difference between the appearance of an animal (called its phenotype) and its genetic makeup (called its genotype). Most commonly encountered discussions of canine coat color are basically phenotypic, as in most cases we can only describe the colors that we see in the dog in front of us.

Here are the basics of dog coat color genetics as I understand them:

First we will discuss a series of genes (the S locus) that control the distribution of color on a dog. Then we will discuss the varies series of genes that control the colors themselves. The A (agouti) locus (which is the principle set of genes that govern distribution of black pigment relative to red pigment in the coat), the various dilution loci, the brindle and black mask loci.

Spotting and white markings

The presence of color in a mammal is due to the presence of granules of pigment in pigment bearing cells called melanocytes. Where melanocytes are present the animal has the potential to produce color. Melanocytes serve an important function in shielding deeper structures from harmful ultraviolet radiation.

The first variable of animal coat color is the distribution of these pigment bearing cells. There are sets of genes that influence the distribution of melanocytes on the body. When these cells are absent, unpigmented white patches appear. If one of these patches of white skin is taken and transplanted into a dark colored spot on the animal the resulting transplant will remain white since it has no pigment cells. Injuries that damage the melanocytes in an area can result in white scars due to failure of these cells to regenerate.

Melanocytes are rather special cells. First they take their embryonic origin from the same part of the embryo and at the same time as the central nervous system (the brain & spinal cord). After the brain and spinal cord are formed these special cells that are left over at the edge of the area of central nervous system formation are called Neural Crest Cells.

These special Neural Crest cells then migrate throughout the body to form the melanocytes of the skin, the adrenal glands, the dentine of the teeth,some of the bones of the base of the skull and the voice box, the cornea of the eye, special sensory cells of the ear and special components of the involuntary nervous system in the viscera.

The genes producing unpigmented white patches on the body do so by interfering either with the total number of neural crest cells produced or with their ability to migrate. In the developing embryo some structures have a stronger attraction for these migrating cells than others and in a sense have a 'priority' on them if they are in short supply. The skin has the lowest priority and this competition for limited numbers of neural crest cells accounts for some of the commonest patterns of distribution of white markings on domestic mammals.

The major series of genes affecting the distribion of melanocytes in dogs are commonly called the "S" or spotting series - alleles that affect the distribution of pigment bearing cells. There is a bit of controversy even here but most workers agree on at least 3 alleles.

Most white dogs are s-w, s-w for color distribution (meaning that they have the extreme white piebald gene (s-w) at this chromosomal site on both the chromosome inherited from the dam and the one inherited from the sire) and then have inherited various of the dilution genes that reduce color intensity so that the few spots that are present are diluted out and not noticable.

Controversies concerning the S series: Irish marked animals bred to spotted animals can produce self-coloreds as well as irish marked and spotted animals. If the above "S" gene mechanism were the only way to produce "Irish", this should not be possible, so there are times when the Irish pattern appears to be due to some other modifiers acting to restrict color in a self-colored dogs.

"T" or ticking series - the dominant gene T allows formation of small speckles or spots of the whatever color the dog is in the areas of the dog that are white due to the action of the S series alleles. The ticking is usually absent at birth and the concentration of ticking can increase with age. Ticking is much more obvious in dogs with a black coat than in diluted cream dogs. Ticked bicolor (black&tan) dogs will have black ticks on the body and tan ticks on the extremities. Heavily ticked animals in pointer breeds are termed "beltons". Ticking is present in Borzoi and helps to produce harder black claws and black foot pads in otherwise white dogs. The mechanism of action of the ticking gene may be similar to the action of the apaloosa gene in horses.

It should be noted that in other breeds of domestic animals multiple loci have been shown to be important in producing spotted animals. In horses there are at least two different loci producing piebalds the overo and the tobiano.

Colors, shades and distribution of color in the coat.

The second great variable in coat color is the shade, intensity and distribution of the colors present in the pigment bearing cells. There are two primary pigments in the coats of mammals, red and black. Outside of spotting all other aspects of coat colors are due to the action of a series of genes that affect:

  1. The presence or absence of one or both of these pigments in the hair and skin.
  2. The degree of dilution of the pigments present.
  3. The patterns of distribution of the pigments within a given hair
  4. The pattern of distribution of different colors of pigmented hairs over the body. We can most easily understand coat color if we first consider color patterns that are the result of these separate actions and then consider the results of these actions taken together. Most canine coat color researchers agree on the presence of the following sets of genes as controllers of coat color in dogs (each set is called a genetic locus - the alternative genes for each locus are called alleles). The alleles are listed in order of most dominant to most recessive. A dominant color will normally mask a color recessive to it. Any given normal animal can have a maximum of only two alleles at a given locus. For each locus I list first the gene name then a physical description of the gene's action.

    I. "A" locus - The Agouti or primary coat color locus

    This locus is the major determinant of color of hairs over whole body unless colored hairs are suppressed by spotting (i.e. piebald or pinto). 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 color which mark alternating episodes during the growth of the hair when the production of black pigment was allowed and then inhibited. The multibanded 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.

    Some "A" locus complications:

    1. A dog that is a-y, a-t will have more black hairs in its coat than a dog that is a-y, a-y. The a-y, a-y dog is called a clear red, the a-y,a-t dog is called a sabled red. This distinction is readily seen in collies and Borzois - breeds in which both red and bicolor (black&tan) exist. The black hairs scattered in the coat will either be all black or black tipped, but not multiply banded.

    2. There is a dilution of a-t which has been called, incorrectly I feel, "agouti". It has also been called silver sable (Borzoi), domino (Afghans) and grizzle (Salukis). In Borzoi, Salukis and Afghans breeders sometimes speak of it is an additional A locus color recessive to black&tan. It was not until I had A (dominant black) dogs to deal with that I was able to see some breedings showing this color to be a dilution of a-t rather than an additional allele on the A locus. In these dogs the vast majority of the hairs are dark tipped, an occasional multi-banded hair can be found.

      If any one animal can have only two alleles on a locus it can be difficult to decide if a third color is due to a third alternate allele for that locus or if it is due to a modifying factor that alters the appearance (phenotype) of only one of the alleles.

    3. Dr Acland pointed out to me that in most mammals the agouti banded wild type is the dominant color of the A locus series. This is not true in dogs, where we have the unbanded dominant black as the most dominant allele. This is actually a major complication. Although it does not falsify the relative inheritance of the colors grouped as being on the "A" locus it does raise the possibility that this locus is not homologous to the A locus common to other species of mammals.

    II. Dilution loci

    - these affect the intensity of pigment in the coat, skin and eyes.

    Dilutions affecting black pigment the most profoundly:

    1. "B" series (two alleles: B,b) - commonly called liver dilute, red dilute or brown dilute - black pigment is lightened and reddened to chocolate, liver or deep red. Red pigments are lightened from red to tan. Liver dobes, Pharaoh hounds and Ibizan Hounds are common examples. I have seen liver dilute Borzoi also but it is very rare and undesired since the noses are definately red to brown.

    The color of skin that is normally black is also affected, as is eye color. The dogs will have yellow eyes and pink to red to chocolate nose leather, lip rims and eye rims. The liver or brown (b) condition is recessive .

    2. "D" series -commonly called blue dilute -(two alleles: D,d) black pigment is diluted to blue, red & yellow pigment is washed out towards silver. The dilute (d) condition is recessive. Blue danes and dobes are common examples. This dilution is more common in Borzoi than liver dilution since a dark grey nose in a white or silver dog is not as markedly light as is the liver nose in a white dog. They eyes are generally lighter than in undiluted litter mates and may be blue at birth darkening to a paper bag colored yellow-gray by a year of age. The nose leather, eye rims and lip edges will be dark grey. Some blue dilute individuals may have acceptably dark eyes. This is probably due to the presence for an independent gene for dark eyes.

    3. "C" series (also called albino and chinchilla dilute) - Black and red pigments are both reduced in amount. Blacks become silvery grey, reds become cream to off white. Several alleles.

    Controversies about these three dilution loci: The B and D series seem to be the major gene loci on which all workers agree. The C series may have more alleles, perhaps minor variants on the c-ch allele, a variant may be responsible for the Borzoi greys that turn gold.

    4. The "E" (extension locus). This is quite controversial. I (BD) feel that there are two alleles -- E, which allows for full expression of black pigment distributed as the dog's A locus genes dictate, and the recesive e, extension yellow, in which all black is supressed in the coat from birth. We have extension yellow in Borzoi.

    5. Many workers put black mask (super extension) and brindle on the E locus. However the presence of black masked but otherwise clear gold dogs argues for a separate super extension (black mask) locus. Black mask has a number of different phenotypes - from the fox black muzzle which may lighten by 3 years of age to the fully black head with black on the toes, chest, tail tip, ears and genital region (sort of a mirror image of the bicolor condition). We have black mask in Borzoi. These could represent different masking alleles.

    6. As for brindle, the clustering of black pigment into stripes wherever the coat is red, I (BD) have a lot of breeding records to indicate that it is a dominant gene that is independent of black mask and does not belong on the E locus. The degree of brindling varies greatly from individual to individual. A brindle can have a few widely spaced stripes or it can be so heavily striped that the base color is seen as only a few pale streaks in an otherwise dark coat. The genetics of this range of brindling intensity are not well understood but are thought to be inherited independently of the presence or absence of brindling.

    7. "G" locus - greying - a dominant gene G that progressively greys black pigment in the coat and a recessive gene g that fails to cause greying. Kerry blue terriers and scottish deerhounds are a good examples of this. Pups are born black, the GG and Gg pups turn blue grey with black nose leather and lip pigment, the occasional gg pup will remain black.

    8."M" - Merle series. Another controversial series that may have several alles. Normal is recessive. M is dominant and in many breeds MM dogs have reduced vigor and the breed commonly has mm normals as well as Mm merles. Colors associated with the M series include merle in collies, merle and harlequin in danes, dapple in dachshunds. The M gene does not occur in Borzoi, fortunately.

    Unexplained mysteries.

    Is there a red intensifier locus responsible for intense red pigmentation in e,e dogs such as Irish Setters, Salukis and greyhounds. Some red Borzoi from the United Kingdom appear to have this intensifier. Little proposed a dominant gene "P" which affects depth of pigment.

    Mahogany sabling - many a-y red dogs are born black, lighten until puberty and then with each new coat lay in more and more black hairs in a distinctive mantle that somewhat resembles the phenotype of the "dominos". However the "dominos" are born domino patterned and do not lighten to an unpatterned state. Mahogany sabling in Borzoi is seen in both dark and washed out (probably c-ch) red dogs and also occurs as an overlay on many brindles, producing a mahogany brindle. My breeding records suggest that the mahogany sable factor is recessive . It is important to remember that the original meaning of the word sable is black. Originally collie fanciers spoke of "sabled reds" that is red dogs with black hairs in their coats, but time and linguisitic shift shortened this to "sable" for a red dog with black hairs. In the interest of linguistic accuracy this usage should be discouraged. "Sabled red" is to be preferred. This mahogany sabling appears to occur in Akitas and Belgian Tervuren (where it is combined with black mask). I have seen it in Borzoi in unmasked individuals.

    "Argent" silvers. This is a dilution of the dominant black. Self colored dogs are born dark silver, being darker on the face and legs. As they mature the entire dog lightens and the body coat becomes a mixture of white, black and grey hairs. I suspect that this is the same dilution acting with the dominant black as the 'agouti' acts with the bicolor (a-t). It may be that the cream sables are this dilution applied to an a-y red.

    Summary of Canine coat colors found in Borzoi

    A locus     color                   B locus              D locus
A           dom black               B       normal       D        normal
a-y         red                     b       brown        d        blue
a-t         bicolor(blk & tn)

E locus                             "SE" locus
E           normal                  SE          black mask
e           extension yellow        se          no mask

"Br" locus                            S locus
Br          striped (brindled)      S           solid colored (self)
br          not striped             s-i         irish marked (collie mrkd)
                                    s-p         spotted
                                    s-e         extreme white spotted

T locus                             G Locus
T           ticked                  G           greying
t           not ticked              g           not greying

C locus 
C           full colored
c-ch        chinchilla dilute
    Remeber that each dog has two genes at each locus. The genes may be identical in which case the dog is homozygous for those genes - or they may be unlike - in which case the dog is heterozygous.

    8 accepted loci, 2 controversial loci for which there is good evidence in Borzoi and the hypothetical mahogany sable overlay condition, a conditon which is well observed in Borzoi and Akitas even though the genetic details are yet to be worked out. It should be noted that all of these loci can occur in different combinations with each other leading to over 4000 possible color combinations.

    Glossary

  5. Dominant - in genetics, the situation in which the presence of a single gene of a given pair will cause the trait or condition to be apparent in the animal.

  6. Homologous - in biology this means similar because of a common structure in the common ancestor. Thus the wing of a bird and the foreleg of a dog are homologous structures since the structures are both derived from the foreleg of a common ancestral primitive reptile. Analogous structures are structures similar due to similar function - as in the flipper of a porpoise and the diving plane of a submarine.

  7. Recessive - in genetics, the situation in which the presence of a single gene of a given pair is not sufficient to cause the trait or condition to be apparent in the animal. Recessive traits are sometimes called hidden traits.

    References and Further Reading

    Starting on Oct 1, 1996 -You are Canine Coat Color Genetics Article visitor number