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 genes, see the pages in the "Colours" section.

Remember, every dog has two genes from each locus. They can have two of the same gene, in which case they're homozygous, or two different genes, in which case they're heterozygous. In most cases, a heterozygous dog will express whichever of its genes 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 A^ya^t (one copy of sable, one copy of tan points) may result in a dog with more black hairs than a homozygous sable (A^yA^y).
Genes 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 eumelanin and phaeomelanin)

- A^y: Sable (red with or without black tipping). Used to be labelled a^y 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!).
- a^w: 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. Very little is known about it, and it's dominance is, as yet, undecided.
- a^s: Saddle-marked (red with black markings on the back, neck and tail). This one is controversial, but many people do believe it exists. Very little is known about it, but it does appear to be dominant over tan points and not over sable. It is possible it has incomplete dominance over tan points, producing creeping tan when a dog has one tan marking gene and one saddle gene, but this is just one theory.
- a^t: 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.

C LOCUS ("albino series", affects intensity of phaeomelanin, and sometimes eumelanin)

- C: Normal pigment. A dog with one copy of the C gene produces normal phaeomelanin (rich red/tan).
- c^ch: Chinchilla. Chinchilla causes lightening of phaeomelanin (red) to light gold or cream, but has no affect on eumelanin (black etc). There may be more than one form of chinchilla, accounting for the extreme variations in shade of red pigment.
- c^e: Extreme chinchilla (or extreme dilution). A stronger form of chinchilla, which causes phaeomelanin (red) to become white, leaving eumelanin unaffected (so eyes and noses remain fully pigmented).
- c^p: Platinum (or ivory). True albino is c, the bottom recessive on the C locus. However, this gene is not thought to occur in dogs. Platinum is thought to occur though, notably in the Dobermann. It dilutes phaeomelanin and eumelanin to almost white (often a creamy shade).

There may be a further gene on the C locus which restricts phaeomelanin to the back, tail, neck and head, leaving white markings placed roughly in the same position as A locus tan markings, as in Shiba Inu. It is possible that this gene is affected by temperature (so restricted to the warmer parts of the dog). The himalayan gene (C^h) is a temperature-affected C-locus gene which occurs on cats, but this results in the opposite effect - colour is restricted to the coldest areas (legs, tail, face).

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)

- E^m: 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 E^m.
- 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 (eumelanin only).
- 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).

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.
- k^br: Brindle (black stripes on a red base). k^br is dominant over k, so a dog only needs one k^br 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).
- sⁱ: Irish spotting (white on muzzle, neck, chest, feet and tail tip). Varies greatly, and there may be an allele which causes less white spotting than this one, but it hasn't been identified yet. There is also thought to be a separate gene that causes "true" irish spotting (much less variable than the general type) in breeds such as the Boston Terrier. This gene has been found in a number of breeds but its relationship to the spotting series and the sⁱ gene is unknown.
- s^p: Piebald (over 50% white, with large pigmented patches on a white base).
- s^w: Extreme white (a piebald with a high percentage of white. Colour generally confined to base of tail and head).
(All of the white spotting genes are thought to have incomplete dominance over one another. This means that a dog with, for example, one gene for no white and one gene for piebald will have an intermediate amount of white - somewhere around the level of irish spotting).

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.
- t: Clear white (no ticking on white areas).

A SUMMARY OF THE SUMMARY

A locus -
A^y - sable
a^w - agouti/wolf grey
a^s - saddle-marked
a^t - tan points
a - recessive black

B locus -
B - non-liver
b - liver

C locus -
C - normal phaeomelanin
c^ch - chinchilla
c^e - extreme chinchilla
c^p - platinum

D locus -
D - no dilution
d - dilution of eumelanin to blue or isabella

E locus -
E^m - black mask
E - normal extension (no mask)
e - recessive red

G locus -
G - greying
g - no greying

H locus -
H - harlequin
h - non-harlequin

K locus -
K - solid black
k^br - brindle
k - non-solid black

M locus -
M - merle
m - non-merle

S locus -
S - no white spotting
sⁱ - irish spotting
s^p - piebald
s^w - extreme white

T locus -
T - ticking
t - no ticking

A locus genes will only be expressed when a dog does not have a dominant black (K) gene. S locus genes (white spotting) appear on top of anything else a dog has - there is nothing that can mask them except for, possibly, C locus genes, which may make them difficult to see. D and B locus genes for liver and dilution will override all genes for black (dominant or recessive) and change all eumelanin on the dog. E locus genes are not overriden by anything except for the C (albino) 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 gene (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:

a^ta^tbbCCddeEggHhkkmmSSTt

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:

a^ta^t - two genes for tan points. So the dog will have tan points.
bb - two genes for liver. So the dog will be liver.
CC - two genes for no dilution of phaeomelanin. So any red on the dog will be a normal, rich shade.
dd - two genes for dilution of eumelanin. So the dog will be blue.
eE - one gene for recessive red, one for normal extension. Normal extension is dominant over recessive red, so the dog will not be recessive red.
gg - two genes for no greying. So the dog will not have greying.
Hh - one gene for harlequin, one for non-harlequin. So the dog will be harlequin.
kk - two genes for non-solid black. So the dog will express its A-locus genes.
mm - two genes for non-merle. So the dog will not be merle.
SS - two genes for no white spotting. So the dog will have no white.
Tt - one gene for ticking, one for no ticking. So the dog will have some ticking.

So our dog will have tan points (which can show through because there is no dominant black gene to stop them from being expressed), it'll be liver, or in fact diluted liver because it is dd, so it'll be isabella. 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 chinchilla dilution of red, no greying, no brindle, no mask and no recessive red.

What we've ended up with is an isabella dog with tan points:

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