Summary of Series
This page is simply intended as a quick reference to show what is on each locus. For more detailed information about the individual allele, see the pages in the “Main Stuff” section.
Remember, every dog has two alleles from each locus. They can have two of the same allele, in which case they’re homozygous, or two different alleles, in which case they’re heterozygous. In most cases, a heterozygous dog will express whichever of its alleles is the most dominant. Ocassionally incomplete dominance occurs (probably in the A locus tan markings and almost certainly in white markings), and this means that the dog expresses the most dominant gene but is also partly affected by the less dominant one. For example, a genotype of Ssp (one copy of the allele for no white spotting, one copy of the piebald allele) may result in a dog with some white markings, but less than a homozygous piebald (spsp).
Alleles are listed roughly in order of dominance. For some locii, this is completely guesswork, and may be incorrect.
Also, remember the two types of pigment – eumelanin (black, liver, blue, isabella), which affects the coat, nose and eyes, and phaeomelanin (red), which affects only the coat. I have specified below which type of pigment is affected by each locus.
A locus (“agouti series”, affects distribution of both eumelanin and phaeomelanin)
– Ay: Sable (red with or without black tipping). Used to be labelled ay when dominant black was believed to be above it on the A locus, but now black has been given its own locus (K) and sable has been promoted to the most dominant on its locus (so has gained a capital letter!).
– aw: Agouti (banded hairs). Like sable above, but the hairs all over are banded with black. This is most likely the gene responsible for wolf grey.
– at: Tan points (black body with red on muzzle, chest, eyebrows, legs and vent). Only dominant over recessive black (below), so a dog needs to be homozygous for tan points in order to express them (or heterozygous for recessive black and tan points, but recessive black is very rare).
– a – Recessive black (solid black with no red in the coat at all).
B locus (“liver series”, affects colour of eumelanin)
– B: Normal pigment. A Bb or BB dog produces normal black eumelanin.
– b: Liver pigment. A bb dog produces liver eumelanin instead of black.
D locus (“dilution series”, affects intensity of eumelanin)
– D: Normal pigment.
– d: Diluted pigment. When homozygous (dd), turns black to blue and liver to isabella.
E locus (“extension series”, affects distribution of eumelanin)
– Em: Masked (black on the muzzle and the ears, and sometimes spreading to black tipping on the chest and/or back).
– E: Normal extension (no restriction of pigment). Usually written with a capital letter, but is in fact recessive to Em.
– Eg: Grizzle/domino (found only in Salukis and Afghan Hounds)
– e: Recessive red (solid red all over, except for white markings). An ee dog is unable to produce any eumelanin (black) in its coat. Any black present will be turned to red. The eyes and nose are, however, unaffected (a recessive red dog may still have a black nose).
G locus (“greying series”, affects how eumelanin keeps its itensity over time)
– G: Progressive greying. A dog with one or two G genes will be born dark-coloured and its hair will lighten over time.
– g: Normal (no lightening of pigment).
H locus (“harlequin series”, modifies merle)
– H: Harlequin. Areas between patches on a merle dog are turned to white, leaving solid pigmented patches on a white base. Only works with merle gene and does not affect non-merle dogs.
– h: Non-harlequin (normal expression of merle).
I locus (“Intensity series”, affects the richness of phaeomelanin)
– alleles not yet known
K locus (“black series”, affects eumelanin)
– K: Black (solid black all over). Overrides A (agouti) series. Any genes on the A locus will not be expressed.
– kbr: Brindle (black stripes on a red base). kbr is dominant over k, so a dog only needs one kbr in order to be brindle (but will be overriden by one K gene). Brindle dogs will express whichever genes are on their A locus, but the red parts of the coat (phaeomelanin) will be brindled (black parts will not be affected).
– k: Non-solid black. A kk dog will express whichever genes are on its A locus.
M locus (“merle series”, affects intensity of eumelanin)
– M: Merle (black patches on a grey base). Dilutes random sections of the coat to a lighter colour, leaving patches of full pigment. Phaeomelanin is not affected – only areas of eumelanin can be merled.
– m: Non-merle (normal expression of eumelanin).
S locus (“spotting series”, affects distribution of all pigment)
– S: No white (all of coat is pigmented – no white spotting).
– sp: Piebald (homozygous causes over 50% white, with large pigmented patches on a white base). Heterozygous piebalds may have varying amounts of white, from none at all to “pseudo-irish” (phenotypically the same pattern as irish spotting but not caused by the same allele)
– si: Irish spotting (white on muzzle, neck, chest, feet and tail tip). This type of white spotting may not actually be on the S locus but I have included it here for lack of anywhere else to put it! Homozygous sp causes irish markings and heterozygous may have any amount of white inbetween solid and irish.
T locus (“ticking series”, affects distribution of all pigment)
– T: Ticking (white areas are ticked with small flecks or spots of colour). Ticking is whichever colour would have been on that area if the dog did not have white. Suspected to be another case of incomplete dominance – a TT dog has heavier ticking than a Tt dog.
– Tr: Roan (more dense than ticking)
– Td: Dalmatian spots (large, round ticking spots)
– t: Clear white (no ticking on white areas).
A Summary of the Summary
A locus –
Ay – sable
aw – agouti/wolf grey
at – tan points
a – recessive black
B locus –
B – non-liver
b – liver
D locus –
D – no dilution
d – dilution of eumelanin to blue or isabella
E locus –
Em – black mask
E – normal extension (no mask)
Eg – grizzle/domino
e – recessive red
G locus –
G – greying
g – no greying
H locus –
H – harlequin
h – non-harlequin
I locus –
K locus –
K – solid black
kbr – brindle
k – non-solid black
M locus –
M – merle
m – non-merle
S locus –
S – no white spotting
sp – piebald
si – irish spotting (may not be on S locus)
T locus –
T – ticking
Tr – roan
Td – Dalmatian spots
t – no ticking
A locus alleles will only be expressed when a dog does not have a dominant black (K) gene. S locus alleles (white spotting) appear on top of anything else a dog has – there is nothing that can mask them except for, possibly, I locus alleles, which may make them difficult to see. D and B locus alleles for liver and dilution will override all alleles for black (dominant or recessive) and change all eumelanin on the dog. E locus alleles are not overriden by anything except for the I (intensity) and S (white spotting) locii, so recessive red will be expressed even on a dominant black dog. Black masks will be expressed also but may not be visible on a black dog. The H locus will only be expressed on a dog with the merle allele (M locus) and the T locus will only be expressed on a dog with white spotting (S locus).
Putting it All Together
Let’s have a quick go at putting all this information together. Here’s a genotype for a dog which we are going to decipher to work out what the dog would actually look like:
That looks daunting, so let’s take each pair of genes individually, referring back to the summary of series above to see what each letter means:
Ayat – one allele for tan points, and one for sable. Sable is dominant over tan points, so the dog will be sable.
Bb – one allele for liver and one for normal expression of eumelanin. So the dog will not have liver pigment, as the liver allele is recessive.
dd – two allele for dilution of eumelanin. So the dog will express blue eumelanin.
eEm – one allele for recessive red, one for a eumelanin mask. Mask is dominant over recessive red, so the dog will have a mask.
gg – two alleles for no greying. So the dog will not have greying.
Hh – one allele for harlequin, one for non-harlequin. So the dog will express harlequin if it is also merle.
kk – two alleles for non-solid black. So the dog will not be solid black and will express its A-locus alleles.
mm – two alleles for non-merle. So the dog will not be merle.
SS – two alleles for no white spotting. So the dog will have no white.
Tt – one allele for ticking, one for no ticking. So the dog will have some ticking.
So our dog will have sable (which can show through because there is no dominant black allele to stop them from being expressed), it’ll be a dilute because it is dd, so it’ll have blue eumelanin. It’ll have the gene for harlequin but won’t express it because it has no merle gene. Likewise, it’ll have the gene for ticking but can’t express that either because it has no white. It also has no no greying, no brindle, and no recessive red, but it does have a mask.
What we’ve ended up with is a blue sable (“fawn”) with a mask:
“Dog Coat Colour Genetics.” Dog Coat Colour Genetics. N.p., n.d. Web. 24 June 2014.