Coat Colors Genetics

by Ragnhild Primdal

Even though colour genetics is well documented, it is nevertheless a mouthful to comprehend correctly, which I hasten to add I do not either!

That apart, I have regardless embarked on the subject of the many colour variations in Tibetan Spaniels, begging forgiveness for any misunderstandings along the way. In addition I am certain I have not been able to accumulate every snippet of information available, thus the text must not in any way be regarded as “the complete works” on the subject of colour genes in our dogs, but if it can stimulate anyone to dig deeper and/or to satisfy curiosity, my objectives are secured.

Dog Chromosomes

Chromosomes

Dog Chromosomes

The colours of our dogs are controlled by genes located on its chromosomes. A canine has 78 chromosomes of which 76 is of the homozygous (biology – hybrid, carrying genes from similar pairs), whilst the two remaining are gender chromosomes, which can be heterozygote (biology – hybrid, carrying genes from different pairs). Most genes are coupled genes, meaning that they are inherited combined. But, the colour of fur, its intensity and location on the individual dog, is located on different chromosomes and is therefore independently inherited.

Alternatives are those that can “reserve space” on the same locus (meaning place, location, as the genes are also called). These are named Allelés (from the Greek αλληλος allelos, meaning each other), and it may never be more than one allele on any one locus on each of the chromosomes in a pair. Often both a dogs phenotype and genotype is discussed. Phenotype is the visible colour and its variations that we see, and genotype is the individuals genetic traits, not necessarily visible and that also carries recessive genes which is controlled by various locuss that makes pale, intensifies, locates, hinders or hide each other.

There is, according to C. C. Little, at least 10 different pairs of chromosomes in a dog, but how many of these are present in a Tibetan Spaniel is not known, at leat not to me. According to Catherine Marley can 8 be found in Lhasa Apsos and it is reasonable to assume the same number is present in our dogs, especially as those two breeds has a common background somewhere in the rather dim past. The sum of the locuses are responsible for the rich variations in colour and patterns we can see in our dogs.

Further on in this article, you will find a table listing all of the alleles assumed to be present in our dogs, hopefully contributing to understanding.

Color Genetics

Color Genetics

Every single individual “Tibbie” has two alleles from each of the assumed eight series og genes. One allele from each series from its mother and one from its father. The basic, genetic types of colours present can be defines as follows.

  1. SableSable (golden, red, creme or grey): It is within this group we will find the greatest number of Tibbies. The colours are a combination of light or dark hairs in various amounts. Light ones varies from deep red to light creme or white. Darker ones are normally black but may also appear liver-coloured or gray, depending on how many plus or minus factors that enters the equation. Some sable dogs loose black or dark strands of hair as they grow older but must not be confused with “clean” colours, that does not have any form of dark markings at birth.
  2. CremePure tan (red, golden, creme or white): These dogs do NOT have a dark pigment in their coats colour (nor black nor liver-coloured), not even at birth.
  3. BlackBlack: A completely black Tibbie will never have red, golden or creme coloured strands of hair anywhere, if so it will not be classified as black but as black & tan, permitted exceptions are white, preferably on its paws or its chest.
  4. Black & TanBlack/tan: It can be difficult to distinguish if a newborn Tibbie is black & tan or just black, as they both may have white socks and other white markings hiding the tan. The best place to determine this is under its tail, white markings are rear in that location, but black & tans normally always shows tan there, if present.

The reason for the various markings and colours is, as mentioned earlier, the individuals various alleles. The dark portion of the pigment can be reduced (modified – a minus-factor), by a large number of other genes.

  1. Parti-colorParticolor-gene (P) is able to change any one of the four basic colours, evident by white markings on the body.
  2. Light BrownGray factor (G), changes dark hair to grey in all basic nuances, as the dog grows older. Only its snout (the forward facing portion of its nose), is independent from this allele.
  3. Red/Black maskBlue gene (d) causes dark or black hair to turn grey, usually visible at a young age. The snout area on a blue puppy is normally grey and the eyes either grey or brown like a nut.

Liver colour (b) may change black elements in all the basic colours including in the snout area which normally turns into liver or brown or, on rarer occasions, yellow.

The lighter pigment in the basic colours can be modified or reduced by another gene; the so called red/golden dilutive factor designated (C), that controls de “depth” of the colour which opens up for it turning into any hue from deep red to a light, creamy white.

So, with this we should be able to evaluate genes, keep in mind though that a series may contain four genes, but any individual dog may only have two genes from each series.

Dark Red/SableThe A-series controls the development of patterns consisting of the DARK (black/brown), and LIGHT (red/golden), coat colours The A-gene is the most dominant in the series. It determine patterns from the dark and light pigment. If the dog carries an A-gene, it will turn black or black & white. If the dog carries an a-gene (opposite an A), it will be born darker than what it will be as an adult. It will also be lighter underneath than on its back.

SableThe ay-gene is recessive relative to “A”, but dominant in relation to the at-gene. The ay-gene is the gene determining how much of the dark pigment will be in the coat, but can be covered up by the A, in which case black dominates. The colour will be sable if the gene stems from ay  or at.

Black/White partiThe at-gene is the most recessive allele in the A-series, in a double dose it gives black & tan, but if the other gene is ay, the dog will be sable, and only if the puppy is given the at-genet from both the sire and dam will it become black & tan. This means that if you mate black & tan with another black & tan, all the offspring will become black & tan, unless modified by for example the parti-gene. In those cases the dog will become tri-coloured but may also appear to be black & white. The dog can also become pure red / creme / golden, if it receives the recessive e from both parents, as ee in double dose prevents the formation of dark pigment in its coat. Even black or sable may produce black & tan, if both parents carries the at  – gene recessively.

A, ay  and A, at  will give black dogs, ay , at  or ay , ay  gives sable, at , at gives black & tan. You will likely never see totally black dogs after two sable dogs, but the chance increases if the parents are in a pure color providing at least one of those are offspring from a completely black dog or a “pure” black & white parti.

Chocolate/TanThe B-series have two alleles, and affects the color of the darker pigment. The B-gene is the allele for black pigment in coat and snout, B is dominant towards b. The b-gene is the recessive allele for livercolour or brown. A puppy will only become liver-coloured or brown, if both parents carries the b-gene. Earlier liver or brown was not wanted in Tibbies, but is now approved as a colour variation.

WhiteThe C-series has four alleles, and affects the color of the lighter pigment. C-gene is therefore the cause of the variations in the sable nuances, from deep red and towards creme or white. C is dominant and gives a deep red or golden colour in the lighter areas of the coat, if such exists.

Silver/SableThe cch –gene (Chinchilla-gene), is the second gene on the dominant scale and reduces red and yellow, but has no effect on black. This gene will be invisible on a black Tibbie. To the contrary it is the gene which is relevant to create silver & sable, which in fact is a red & sable dog where the red has gone pale due to the c ch   - gene. The ce   –gene is the most recessive gene in the series, giving an extreme, pale red. Even if the dog has a dominant C-gene it will nevertheless give a considerable bleaching of even very dark colours. The dog will with Ce , even if its golden, become crème & white. In a double dose the ce ce becomes almost albino. Nose and eye pigmentation is diluted and any black hair in the coat will change towards a pale grey. ca  -gene is the albino gene, where no colour exists, not even on lips, nose or the edge of the eyelid. Even the eye will be “redish” in a pure albino, because there is no pigment to obscure the capillaries inside the eye itself. The surface of its skin will be pink.

Red/SableThe D-series has two alleles, affecting the darker areas in the coat (as C controls the light pigment). The D-gene is dominant, whilst the d-gene is recessive. D provides a deep, concentrated pigment in hair, nose and in the irises of the eyes, whilst d contributes to ”blue”, which is actually a dilution of the pigment. A completely black and a deep red Tibbie is probably examples of a DD or Dd combination. I am not familiar with a “blue” Tibbie, which typically would be a dd, thus maybe D is only found as a homozygous chromosome in a Tibbie?

The E controls the production of dark pigment (liver or black). The E-gene is the reason for seeing such a wide variety of colour patterns in Tibbies. The genes E and A affects each other a great deal, therefore it is hard to tell if a colour and/or pattern is caused by A or by E.

Black maskThe Em-gene is the most dominant, it spreads the dark pigment whereas the pattern-gene, A, will order Em  to carry this out. It is also thanks to Em   that many of our dogs have a dark mask. A dark mask cannot be seen in a black dog of course, but will be evident in a sable or black & tan. E produces dark pigment ( as directed by A), without a mask. E is recessive to Em , but dominant to e. The e-gene is recessive to both Em and E. e cannot produce dark pigment. Even if the A-gene for black is present, the dog will not have dark or black hair, because the e-gene does not produce dark pigment, which is required for A to work. All dogs having ee will become pure red, golden, créme or white, regardless of other genes. Only a parti-color gene can be “visible” in this phenotype. On the other hand i may appear completely black puppies from mating two golden/créme/sable individuals, providing they have the genes ee-AA (creme / pale golden, as e prevents the black from A), and ayay EE (sable), which will give the puppy the gene-combination Aay  – Ee. Because A is dominant realtive to ay , and E is dominant relative to e, the pattern-gene A (pure black) may benefit from Es’s production of pure black.

GoldenThe G determines if a color goes paler with age. The G-gene is dominant and becomes evident by the darker colours going paler with age (the dog gets grayer). Darker colours do not go pale, providing the dog does not carry the g-gene. The g–gene is recessive. G will nevertheless appear somewhat different, depending on the dogs gene-pool, especially from some of the B and D – series of genes.

The S locus determines white patterns S-gene is the most dominant gene and means the coat will be in one colour.

Tri-colorThe si-gene produces just small amounts of white and is recessive to S. It is also called Irish Spotting, which means there are small amounts of white on the paws or chest. sP is the gene responsible for a typical parti-color pattern, the majority of the dog is white. Usually only about ¼ of the dog is coloured, but due to the plus and minus factor that plays a part in the production of pigment in this locus, it can be difficult to decide if the gene actually is sP  or si . sP is also called Piebald Spotting.

Parti-colour with a little color on the headThe sW-genet is the most recessive gene. It produces extreme amounts of white and quite often the dog only has small, coloured markings around its eyes or on its head, ears or tail. sw   will, in combination with S or si , give atypical parti-color patterns. According to Ms. Catherine Marleys article on Lhasa Apso, she writes that the sw  –gene often appears together with deafness in the inner ear (cochlea). I know of two cases like this in Tibbies. But according to a Norwegian canine medical book called: ”Hund, Avl og Helse” (Dog, Breeding and Health), written and published by the association for veterinary practice on small animals, there are no hereditary defects tied into this gene, but instead to the M-gene, which in double doses can cause deafness and sometimes even blindness and sterility. I have not been able to find out which source is correct.

Tibbie with tickingThe T-gene determines if spots appear = ”the ticking factor”. The T-gene is dominant and produces ”ticking”, more or less clearly seen coloured spots inside white areas, and is produced by the S-gene. These spots first become evident as the puppy gets somewhat older. The t-gene is recessive and does not produce ”ticking”.

Analyzing Coat Colours

Analyzing Coat Colours

A litter can tell a lot about your dogs genetic characteristics, which can be of great help in your breeding program.

Catherine Marley writes (about Lhasa Apso): ”I mated a sable dam with a red & sable sire. Of seven offspring three was black & tan, three was sable and one was a clear golden”. From this I can deduce:

  1. Both parents are sable, thus they must have ay  and an E.
  2. Since I had atat   and ee – puppies, both parents must also carry atand e.
  3. There was noe blue or diluted créme puppies, meaning the parents must each carry at least one C and one D. The male is deep red, and should therefore be CC. The dam is somewhat lighter therefore more than likely a Ccch   .
  4. There was no particolour puppy thus S or si must be present in both the parents.
  5. The dam is greyish, so she must have at least one G. The sire is not greyish and is therefore gg.
  6. The sire has produced brown noses before but not in this litter, which makes it certain it is a Bb. As there where no brown snouts in the litter it must mean that the dam, possibly, is a BB.

When putting all these factors together I am able to work out a complete list for both the parents and their offspring.
- sire: ay at Bb, C(C?), D(?), Ee, gg, S(si )
- dam: ay at, B(B?), Ccch   , D(?), Ee, G(?), S(si )

genes

click to view larger image

When I am mating this dam again, I can avoid black & tan puppies by mating her with a sire that never has produced black & tan, not even when he has mated with a black & tan dam. (This “proves” that he was homozygous in relation to ay ay and that he did not carry at gene.) To avoid pure coloured puppies I had to find a sire that had been mated with a pure coloured dam that had never produced pure colour puppies. This way I can be sure that my dam will not carry liver colour recessively and I can therefore mate her with known carriers of liver colour without giving a thought to having liver-coloured puppies. If you feel this type of analyses is somewhat technical feel free to use any of the following descriptions concerning colour breeding.

  1. If two animals with identical, recessive patterns are mated, the result will be the same: Black & Tan x Black & Tan = Black & Tan. Unless they carry e, that in double dose prevents the formation of black pigment. If they carries parti, the puppies can be tri-colour.
  2. Recessive, white spots in a massive and extreme version, can cover all patterns. Pure golden recessive (ee), can cover all A-series patterns (pure colour, sable and black & tan), you will never know what a pure colour golden carries in relation to the dark pigment patterns, unless you test your breed in a laboratory.
  3. A black & tan with a deep and well developed “tan”- pattern, will produce a large portion of good red puppies, when mated with a sable.
  4. A pure and true black will produce black regardless no matter who it mates with.
  5. Two red & sable can produce any colour except pure black.