SSCNC: Sheltie Colors

The Colors of The Sheltie

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Color Basics

Sable

Black

Blue Merle

Sable Merle

Tan Points and Bi-color

White Markings

Color-headed Whites

Double Merles

Color Inheritance

Color Inheritance

Our knowledge of color inheritance in Shelties has increased dramatically with the advent of DNA studies. Some of the color genes described by Clarence Little (The Inheritance of Coat Color In Dogs) have been confirmed, others have been disproven, changed or added. There are three major sets of genes responsible for color inheritance in the Sheltie. Genes are simply locations on chromosomes which produce certain characteristics. Variations within a single gene are called alleles. Genes are located on chromosomes, which come in pairs, one gene to a chromosome, so each dog has a pair of alleles for each gene.

DNA Studies: The gene responsible for the A or Agouti series colors has been identified on canine chromosome 24. Each of the four color variants that have been identified (three are present in the Shetland Sheepdog) is associated with point mutations in the DNA which lead to changes in the Agouti protein. The gene for dominant black, formerly designated A, has not been found in the agouti series, and is now considered to be the dominant gene at the K series locus.

Other Sheltie Color Genes

M Locus genes: The M Locus produces the merle pattern. In the Sheltie, this is the locus responsible for irregularly diluting patches of black hair to blue-grey.

The M gene technically has incomplete dominance, because the heterozygote (Mm) can be visually distinguished from the homozygote (MM). A double, or homozygous, merle is MM. Such a dog is predominantly white, and usually has defective hearing or vision. Blue merles, with or without tan points, and sable merles are Mm. Non-merle Shelties are mm. There is some overlap in the amount of white between Mm and MM dogs. In both Australian Shepherds and harlequin Great Danes, a few individuals, with enough color that they would be expected to be heterozygous Mm blue merles, have turned out to be genetically MM double merles.

The Cryptic Blue: The cryptic blue is a dog who at first glance appears to be a tricolor or bi-color black. Close inspection usually shows small amounts of merling. The dog is an Mm dog, who produces blue merle offspring like any other blue merle Mm dog. I asked an Australian Shepherd breeder whether cryptic blues occur in that breed. The answer was, "Yes, and sometimes the blue comes off with the tail dock."

DNA Studies: The gene responsible for the M or Merle pattern has been identified on canine chromosome 10, and is an SILV gene, an important color gene in many other mammals. It is not a point mutation, but is an insertion of roughly 253 base pairs into the DNA of the SILV gene. This inserted sequence of DNA is apparently fairly fragile and can be damaged (shortened) during cellular reproduction. Dogs which carry this shortened form of the insertion are NOT merles and are genetically unable to produce merle offspring. This is the likely explanation for the occasional tricolor offspring of a double merle.

Other Sheltie Color Genes:

B Locus

C Locus

D Locus

E Locus

Major Sheltie Color Genes:

A Locus

M locus

S Locus

G Locus

K Locus

T Locus

A Locus genes: The A or agouti locus produces the so-called Agouti Series colors. In the Sheltie, this is the locus responsible for the sable, black and tan, and recessive black colors. Although three variants of the gene are found in Shelties, each individual Sheltie can carry only two of them. White is superimposed on all of these colors, and is inherited independently of them.

Within the A series genes, sable is dominant to black and tan, and to black. Black and tan is dominant to black. The gene for sable has been designated a^y, the gene for black and tan is a^t, and the gene for recessive black is a. A Sheltie who carries at least one a^y allele will be sable. If both alleles are a^y, the dog is pure for sable and can produce only sable offspring. If one allele is a^tor a, the dog can produce tricolor or black and white offspring when bred to a dog who also has at least one a^t or a allele. Such a sable is tri-factored or bi-factored.

A Sheltie who carries two a^t alleles or one a^t and one a allele will be a tricolor. A Sheltie who has two a alleles is a bicolor black.

S Locus genes:The S locus results in white markings on the dog. Researchers have only started to identify the genes responsible for these markings. It is possible, if not likely, that several different genes act together to produce varying degrees of white markings. The S locus as described by Clarence Little and others is simply one working hypothesis of how white markings are inherited. But in the absence of knowledge at the DNA level, the S locus provides a good description of the inheritance of white in the Sheltie.

In the Sheltie, the S series is used to describe the inheritance of the so-called Irish pattern of white markings around the collar, and on the face, chest, legs and underbelly. This locus is also responsible for white body spots and color-headed white Shelties. Three variants of the gene are described in Shelties, with each individual Sheltie carrying a maximum of two of them. A fourth allele, producing a self-colored dog with no white markings, is apparently no longer found in modern Shelties.

According to Little's model, the allele for Irish markings is incompletely dominant to the alleles for both piebald spotting and extreme piebald spotting. Piebald spotting is incompletely dominant over extreme piebald spotting. The gene for Irish markings has been designated sⁱ, the gene for piebald spotting is s^p, and the gene for extreme piebald spotting is s^w. A Sheltie who carries at least one sⁱ allele will have some degree of typical Irish white markings. If both alleles are s^p, the dog can be expected to have white body spots or to be a heavily marked color-headed white. If one allele is s^p and the other s^w, or if both alleles are s^w, the dog will be a lightly-marked color-headed white.

Expected Colors in a Litter:	Sire:	a^ya^y Pure for sable	a^ya^t Tri-factored sable	a^ya Bi-factored sable	a^ta^t Pure for tricolor (or blue merle)	a^ta Bi-factored tricolor (or blue merle)	aa Bi-color black (or bi-color blue merle)
Dam:		a^ya^y Pure for sable	a^ya^t Tri-factored sable	a^ya Bi-factored sable	a^ta^t Pure for tricolor (or blue merle)	a^ta Bi-factored tricolor (or blue merle)	aa Bi-color black (or bi-color blue merle)
a^ya^y Pure for sable		100% a^ya^y	50% a^ya^y 50% a^ya^t	50% a^ya^y 50% a^ya	100% a^ya^t	50% a^ya^t 50% a^ya	100% a^ya
a^ya^t Tri-factored sable		50% a^ya^y 50% a^ya^t	25% a^ya^y 50% a^ya^t 25% a^ta^t	25% a^ya^y 25% a^ya^t 25% a^ya 25% a^ta	50% a^ya^t 50% a^ta^t	25% a^ya^t 25% a^ya 25% a^ta^t 25% a^ta	50% a^ya 50% a^ta
a^ya Bi-factored sable		50% a^ya^y 50% a^ya	25% a^ya^y 25% a^ya^t 25% a^ya 25% a^ta	25% a^ya^y 50% a^ya 25% aa	50% a^ya^t 50% a^ta	25% a^ya^t 25% a^ya 25% a^ta 25% aa	50% a^ya 50% aa
a^ta^t Pure for tricolor (or tan-pointed blue merle)		100% a^ya^t	50% a^ya^t 50% a^ta^t	50% a^ya^t 50% a^ta	100% a^ta^t	50% a^ta^t 50% a^ta	100% a^ta
a^ta Bi-factored tricolor (or tan-pointed blue merle)		50% a^ya^t 50% a^ya	25% a^ya^t 25% a^ya 25% a^ta^t 25% a^ta	25% a^ya^t 25% a^ya 25% a^ta 25% aa	50% a^ta^t 50% a^ta	25% a^ta^t 50% a^ta 25% aa	50% a^ta 50% aa
aa Bi-color black (or bi-color blue merle)		100% a^ya	50% a^ya 50% a^ta	50% a^ya 50% aa	100% a^ta	50% a^ta 50% aa	100% aa

Expected Colors in a Litter:	Sire:	M M Homozygous (double) merle	M m Blue merle, bi-blue and sable merle	m m Non-merle sable or black
Dam:
M M Homozygous (double) merle		100% M M	50% M M 50% M m	100% M m
M m Blue merle, bi-blue and sable merle		50% M M 50% M m	25% M M 50% M m 25% m m	50% M m 50% m m
m m Non-merle sable or black		100% M m	50% M m 50% m m	100% m m

Since the genes that produce white markings have, for the most part, not been identified, the term white-factored is an approximation that allows rough estimates of the likelihood of an individual Sheltie producing mismarked or color-headed white offspring. Small white body spots may sometimes be an accident of development rather than a reflection of the dog's genetic make-up. It is unlikely that the two Shelties pictured below have the same white color alleles, although both fall within the range of Irish white markings.

NOTE: Since the genes for white markings in the Sheltie have not been determined at the DNA level, the following chart gives approximations only. The Sheltie with a small white body spot is unlikely to be genetically the same as a white with no color except on the head. The continuous gradation of color, from a nearly solid colored Sheltie to a Sheltie with color only on the head, make it likely that several genes act together to determine the amount of white in the coat.
Expected Colors in a Litter:	Sire:	Non-White Factored	White-Factored	Color-Headed White
Dam:
Non-White Factored		100% Non-White Factored	50% Non-White Factored 50% White-Factored	100% White-Factored
White-Factored		50% Non-White Factored 50% White-Factored	25% Non-White Factored 50% White-Factored 25% Color-Headed White	50% White-Factored 50% Color-Headed White
Color-Headed White		100% White-Factored	50% White-Factored 50% Color-Headed White	100% Color-Headed White

DNA Studies: This past year, one gene for producing white markings has been identified on canine chromosome 20. The gene is the MITF gene, also known to produce white markings in other animals. So far, this has been shown to produce white markings in Beagle crosses, Landseer Newfoundlands, and Boxers. The extent to which changes in this gene control the white markings of Shelties is unknown.

B Locus genes: The dark pigment of the dog is termed eumelanin. The genes at the B Locus determine whether the eumelanin is black or brown. There are many confusing names for the brown color. Chocolate Labradors, liver German Shorthairs, brown Newfoundlands, and red Australian Shepherds are all homozygous for the recessive brown allele. The gene affects the color of the skin as well as that of the coat, so that a homozygous recessive dog has a brown nose and eye rims as well as a brown coat. The Sheltie is uniformly black, which is the dominant condition. The recessive brown is only rarely seen in Shelties. See the photo on Sue Bowling's website.

DNA Studies: The B locus is the TRYP1 gene on canine chromosome 11. TRYP1 is short for Tyrosinase Related Protein 1, which is a determinant of coat color in many other species. The dominant B allele results in the production of black rather than brown eumelanin. There are actually three different recessive alleles termed b^c, b^d, and b^s, each acting a bit differently, but any combination of two of them will result in the production of brown eumelanin rather than black.

C Locus genes: The C locus was described by Little as causing progressive dilution of both black/brown pigment and red/yellow/tan pigment to the point where the most recessive allele caused complete albinism. This description was based on genes that exist in mice, and their exact location and function in the dog is not clear. That there are several genes that dilute both kinds of pigment is clear. Whether they correspond to Little's C locus is not clear at all. In the Sheltie, the dominant gene for full pigmentation appears to be the only one routinely found.

D Locus genes: In the Sheltie, the recessive gene at the D locus causes the dilution of black pigment to grey. This recessive gray is present at birth and is seen as a dog with dark gray nose and eye rims, and the black portions of the coat diluted to dark blue-gray. It has no effect on the tan pigment of a sable coat, although it can result in a grey-nosed sable. This is the gene that is called the Maltese blue dilution. It produces a tricolor who is grey, tan and white, and a bi-color who is grey and white. The effect is very pretty, but not currently allowed by the breed standard.

A Sheltie who has at least one dominant D allele will have black pigment. In a Sheltie who has two copies of the recessive d allele, the black is changed to a dark blue grey color. Unlike the merle gene, the dd dilution does not produce a mottled coat. There is a uniform shade of gray in the parts of the coat that would otherwise be black. Photos of a blue dilute tricolor can be seen on Sue Bowling's website.

DNA Studies: The blue dilution is associated with mutations at or near the MLPH gene on canine chromosome 25. Several mutations have been identified, but they are not consistent from breed to breed. Therefore the DNA test that has recently become available to identify carriers of the blue dilution will be reliable only for the breeds for which it was developed. The gene has not yet been examined in the Sheltie.

Expected Colors in a Litter:	Sire:	D D Pure for black pigment	D d Carrier for blue dilution	d d Dilute blue
Dam:
D D Pure for black pigment		100% Pure for black pigment	50% Pure for black pigment 50% Carrier for blue dilution	100% Carrier for blue dilution
D d Carrier for blue dilution		50% Pure for black pigment 50% Carrier for blue dilution	25% Pure for black pigment 50% Carrier for blue dilution 25% Dilute blue	50% Carrier for blue dilution 50% Dilute blue
d d Dilute blue		100% Carrier for blue dilution	50% Carrier for blue dilution 50% Dilute blue	100% Dilute blue

DNA Studies: The E locus gene has been identified as the MC1R gene on canine chromosome 5. The mask is due to a single amino acid substitution coded by the gene, and recessive yellow/red is due to a premature stop codon. This last is a mutation that stops amino acids from being added to a protein, thus resulting in a non-functional protein. The gene for the brindle pattern has NOT been found at this location, and has been re-assigned to the K locus.

E Locus genes: The E locus genes are extremely important in many gun dog breeds. Three alleles are present. The most dominant allele is E^m, which results in a black muzzle, and permits black hair anywhere on the body. Recessive to E^m is the E allele, which is the common allele in Shelties, which allows black pigment to form anywhere in the hair coat. The recessive e allele, which is not found in Shelties, prevents any black/brown pigment from forming in any part of the coat, so that the dog is uniformly red or yellow. Black pigment is still present in the skin. The ee genotype is found in yellow Labrador Retrievers.

Although the E locus has not been analyzed in the Sheltie, it is very possible that the dominant E^m allele is responsible for the occasional "smutty" muzzle seen in Shelties if the white markings do not hide it.

G Locus genes: This is the greying gene which results in a dog who is born black, but who whose black gradually is replaced by a uniform grey color as the dog matures. The breed most characteristically associated with this gene is the Kerry Blue Terrier.

Sheltie are uniformly gg, and their coat remains retains full depth of color as the dog matures. The dominant G allele, not found in Shelties, results in a coat where the black (or liver brown) becomes grey as the dog matures.

K Locus genes: The dominant black gene belongs at the newly described K Locus. The dominant allele results in black dog. This is the common black of the Border Collie. Recessive to black is brindle, and recessive to brindle is non-brindle tan. Brindle is a pattern of vertical black stripes on a tan background, so it can only show on areas of the dog that would otherwise be sable tan.

Expected Colors in a Litter:	Sire:	B B Pure for black eumelanin	B b Brown-factored black	b b Brown eumelanin
Dam:
B B Pure for black eumelanin		100% Pure for black eumelanin	50% Pure for black eumelanin 50% Brown-factored black	100% Brown-factored black
B b Brown-factored black		50% Pure for black eumelanin 50% Brown-factored black	25% Pure for black eumelanin 50% Brown-factored black 25% Brown eumelanin	50% Brown-factored black 50% Brown eumelanin
b b Brown eumelanin		100% Brown-factored black	50% Brown-factored black 50% Brown eumelanin	100% Brown eumelanin

The K locus interacts with the alleles of the A Locus. A dog carrying one or two K^B alleles will be uniformly black, and unable to show the A series sable and tricolor patterns. A dog without the K^B allele, carrying one or two copies of the k^br allele will show the sable and tricolor patterns of the A series, but the tan areas will be brindled. Thus, a sable will appear brindle, and a tricolor will be black, brindle and white. A recessive black (aa) will no show any evidence of brindling regardless of the K Locus genotype, because he has no tan on which the brindle can operate. The Sheltie is almost universally k^yk^y in genotype, so that the A series tan has no brindling.

There are three ways that a dog can carry a k^br gene and not be brindle:
1. It can be ee at the E Locus, and therefore have only yellow/red pigment in its coat.
In technical terms, ee is epistatic to genes of the K Locus and A Locus. The e allele is not known to occur in Shelties.
2. The dog can be K^Bk^br, carrying brindle as a hidden recessive. The K^B allele is not known to occur in Shelties.
3. The dog can be aa at the A Locus (eg. a black and white Sheltie), and therefore have no tan pigment for the brindle gene to affect.

Since Shelties do not appear to carry dominant black, K^B, since they do not carry the recessive e allele, and since the recessive black has only recently gained acceptance as a color, a hidden brindle is extremely unlikely.

Expected Color of the A series tan in a Litter:	Sire:	K^BK^B Pure for dominant black	K^Bk^br Dominant black, carrying brindle	K^Bk^y Dominant black, carrying tan	k^brk^br Pure for brindle	k^brk^y Tan-factored brindle	k^yk^y Pure for tan
Dam:		K^BK^B Pure for dominant black	K^Bk^br Dominant black, carrying brindle	K^Bk^y Dominant black, carrying tan	k^brk^br Pure for brindle	k^brk^y Tan-factored brindle	k^yk^y Pure for tan
K^BK^B Pure for dominant black		100% K^BK^B	50% K^BK^B 50% K^Bk^br	50% K^BK^B 50% K^Bk^y	100% K^Bk^br	50% K^Bk^br 50% K^Bk^y	100% K^Bk^y
K^Bk^br Dominant black, carrying brindle		50% K^BK^B 50% K^Bk^br	25% K^BK^B 50% K^Bk^br 25% k^brk^br	25% K^BK^B 25% K^Bk^br 25% K^Bk^y 25% k^brk^y	50% K^Bk^br 50% k^brk^br	25% K^Bk^br 25% K^Bk^y 25% k^brk^br 25% k^brk^y	50% K^Bk^y 50% k^brk^y
K^Bk^y Dominant black, carrying tan		50% K^BK^B 50% k^brk^y	25% K^BK^B 25% K^Bk^br 25% K^Bk^y 25% k^brk^y	25% K^BK^B 50% K^Bk^y 25% k^yk^y	50% K^Bk^br 50% k^brk^y	25% K^Bk^br 25% K^Bk^y 25% k^brk^y 25% k^yk^y	50% K^Bk^y 50% k^yk^y
k^brk^br Pure for brindle		100% K^Bk^br	50% K^Bk^br 50% k^brk^br	50% K^Bk^br 50% k^brk^y	100% k^brk^br	50% k^brk^br 50% k^brk^y	100% k^brk^y
k^brk^y Tan-factored brindle		50% K^Bk^br 50% k^brk^y	25% K^Bk^br 25% K^Bk^y 25% k^brk^br 25% k^brk^y	25% K^Bk^br 25% K^Bk^y 25% k^brk^y 25% k^yk^y	50% k^brk^br 50% k^brk^y	25% k^brk^br 50% k^brk^y 25% k^yk^y	50% k^brk^y 50% k^yk^y
k^yk^y Pure for tan		100%k^brk^y	50% K^Bk^y 50% k^brk^y	50% K^Bk^y 50% k^yk^y	100% k^brk^y	50% k^brk^y 50% k^yk^y	100% k^yk^y

That Sheltie in the Window: Several years ago, a brindle and white puppy who appeared to be a purebred Sheltie was seen at a pet store. According to our present knowledge, there are only four possible explanations for this:

1. The puppy was not a purebred Sheltie.

2. The puppy was a Sheltie, and at least one of its parents was actually a brindle (both were registered as sable and white.)

3. The puppy was a Sheltie, and the brindle color was the result of a mutation.

4. The puppy was a Sheltie, and the brindle gene had been carried through successive generations of recessive black and white (or blue merle and white) Shelties, aa in genotype, since the origins of the breed without ever being expressed. This explanation is less than satisfactory in view of the stated colors of the parents and the relatively low frequency of the a allele in the breed.

DNA Studies: The K locus gene has been mapped to canine chromosome 16. The gene is a beta-defensin gene, which plays an important role in immunity in several species. It has never before been shown to affect pigmentation.

This page was last updated: November 16, 2011

T Locus genes: The gene or genes that cause ticking and roaning have not been identified. There may well be more than one gene onvolved. Dogs who carry the recessive t gene are born without ticking and remain so throughout their lives. A dog who carries at least one copy of the dominant T gene will develop various amounts of ticking or roaning in the white parts of his coat. If there is only one main gene causing ticking or roaning, there are probably several genes that modify the amount and distribution of the color.

Most Sheltie are tt, and the white parts of their coat remain white throughout life. A few carry the T gene and develop colored ticks in the white hair, which is usually most obvious an the feet, legs and face. It is unknown whether the amount of ticking is influenced by whether the dog carries one of two T genes.