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Author Topic : FYI Color Genetics Explained
 Arden_Farms
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7/16/2008 2:56:03 PM reply with quote send message to Arden_Farms Object to Post   

First the basic genetic types of coat color.

SOLID BLACK:
No red, gold, or cream hair. They may, however, carry white markings. Any dog who appears black, but has any golden hairs on him, especially on the face, feet, or under the tail, is not a genetic black, but a black and tan.

CLEAR TAN (red, gold, cream, or white):
No dark pigment (black or liver.

BLACK AND TAN
black and tan

SABLE (red, gold, cream or grey)
composed of a mixture of light and dark hair in varying proportions. The color of the light hair can vary from red to light cream or white. The dark hair is usually black, but can be liver or grey, depending on the genetic modifiers present. Any red, gold or cream dog, born with any degree of dark tippings or overlay, is a genetic sable.

BRINDLE (red, gold cream)
born with distinct irregular stripes of black on a lighter background, but the pattern usually becomes indistinct in the adult.



The DARK pigment of these basic coat colors can be modified by several other genes:

The particolor gene can change any of these four basic coat colors to the particolor equivalent, by adding white areas to the basic color.

The greying factor can turn the dark hair of any of these colors grey with increasing age. The noses remain black in the case of the greying factor.

The blue gene will also cause greying of the dark hair but it will be detectable in the young puppy. The nose of a blue puppy is usually grey, and the eyes are grey or hazel.

The liver gene can change the black parts of all four coat patterns, including the noses, to liver or brown. The eyes also are usually a lighter brown or yellow.

The LIGHT pigment of these basic coat colors can be modified by another gene:

The red/gold dilution factor controls the depth of red/gold pigment from deep red to pale cream/white
 Arden_Farms
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7/16/2008 3:04:27 PM reply with quote send message to Arden_Farms Object to Post

Now we can consider the actual genes

(Remember that a series may contain four genes, but each animal can have only two genes from each series.)


I. The K series controls the distribution of the DARK coat pigment.
K:­ The "K" gene is the most dominant in this series. It causes dark pigment to be distributed in a "solid" pattern. If one "K" gene is present, the dog's black pigment, if he has any, will cover the body in a solid pattern. i.e. solid black.

Kbr: This is the Brindle factor. It is recessive to K but dominant to the third allele in the series, "k"

k: This gene causes the dark hairs in the coat to be neither solid coverage (black) nor clumped as brindle, but to be distributed in another of two patterns under the control of another locus - the "A" locus.
II. The A series controls the patterning of the dark areas of the coat.

Aw: This pattern of black pigment in the hair is seen in wolves and some northern breeds, and consists of dark and light bands on the individual hairs.

ay: The ay gene is recessive to "Aw", but dominant to the next gene in the series. ay causes the dark pigment to be distributed in the "sable" pattern. ay can be "covered up" if the dog's other gene (of this series) is "Ay". In this case the "wild" pattern would dominate. (The distinction between "sable" and "wild" is questionable however, since I find very little to distinguish the two.) The dog will be sable if its other A ­series gene is ay or at . The dominant black gene "K" will obscure the ay pattern of a sable dog if it is present, since sable depends on k.

at:­ This is the most recessive allele in the A series. It produces the black and tan pattern. It can be covered up by both Awand ay . Aw,ay and Aw,at will both be "wild" wolf colored. ay,at will be sable. Only at,atwill be black and tan. Thus black and tan can be carried as a recessive by both solid true blacks and by sables. Black and tan pups may result from mating a sable to a sable, but a true black never comes from a sable x sable mating unless it is the rare recessive a black. True black can result from a sable x clear mating, if one of the ancestors of the clear parent was a true"K" black. (or true black parti.) If the brindle gene is present it will cause the brindle pattern to appear in the tan areas of the coat. The other possibility producing a black from sable parents is if both parents carry the recessice black "a" gene.

a: This gene is the recessive form of black. It causes an inability of the animal to manufacture the tan form of melanin "phaeomelanin"- it can only make the black "eumelanin", so the animal will be solid black over all the pigmented parts of the body.

III. The B series has only two alleles affecting the COLOR of the DARK pigment.

B - is the allele for black pigment in coat and nose, and is dominant to b.

b - is the allele for liver or brown, recessive to B. Again, B will cover up b. A liver puppy will only result if there are two b genes, one from each parent. In the case of such a liver puppy, each parent had to be either Bb or bb.

IV. The C series has three alleles. C acts on the LIGHT areas of the coat to cause the variation from red to cream or white.

C is dominant and produces full red or deep gold pigment in the light areas of the coat (if there are any).

cch is the next in order of dominance, and causes dilution of the red or gold to cream. Of course this gene would be invisible on the solid black animal, because it has no light areas where the gene can act. cch has less effect on the dark hair than on the light hair. Any grey sable, or "silver" is simply a red sable whose red hair has been bleached out by the action of cch .

ce is the most recessive and causes extreme dilution of red. In a single dose, in combination with C, it can cause some dilution, even though C is dominant. In fact, the whole "C" series exhibits incomplete dominance, so that a Ccch will be slightly lighter than a CC, and a Cce will resemble a cchcch. In double dose (cece), there will be a condition of near­albino color, with reduction of dark pigment as well as light. Nose and eye pigment is diluted, and any black on the coat will be reduced to pale grey.

V. D is the gene for dilution of DARK pigment. (Just as C controlled the light pigment)
D is dominant and gives deep concentrated dark pigment on the hair, nose and iris of the eye.

d is recessive and causes the so called "blue"dilution, as seen in the blue Great Dane. The blue dilution is evident in the very young puppy and is characterized by a slate color of the black areas of the coat, a slate grey nose and grey or hazel eyes. The Weimarener is an example of dd acting on liver pigment to produce that peculiar silver­blue liver color.

VI. E controls the production of DARK (black or liver) pigment. (This pigment will be distributed according to the directions of the pattern gene, A.) The decision of whether or not to make ANY dark pigment, on which A can act, belongs to the E series.
Em In is the most dominant, and produces dark pigment anywhere the A series tells it to. In addition, it produces a black (dark) mask. The mask will be invisible in the solid black pattern, but will be evident in the sable and black and tan patterns.

E also causes production of dark pigment, under the direction of the K and A series, but without the mask. It is recessive to Em, but dominant to e.


e is recessive to both Em, and E and prevents production of any dark pigment anywhere in the hair coat. Even if the K and A genes for solid dark pigment is present, the animal will have no dark hair. This is because no dark pigment is produced, on which the pattern genes, K and A, can act. Every dog who is ee in genotype will be a clear shade of red, gold, cream or white regardless of the other genes he may have. Only the particolor gene can express itself in the ee dog, (pale gold and white). Because all the dark pattern dominants are hidden in the ee gold, the solid pattern KA will not be seen. When such an ee KA cream is mated to an ayay EE sable, the K's, A's and the E's get together, producing a true solid black litter (K?, Aay ,Eech). This is the only instance where a true black can be born of a gold x gold mating.

VII. G is the greying factor. This is the gene which turns the Yorkshire and Kerry Blue Terriers' black puppy coats to the mature blue­grey shade. In contrast to the D gene, these pups have black markings and black noses. The change to grey is progressive with maturation, but the noses stay black.
G is dominant, and causes greying.

g is recessive and causes little or no greying with maturity.
VIII. S is the factor controlling white spotting. Like the C series, the dominance of the S series is incomplete.
S is the most dominant and produces solid coats, In breeds such as Irish Setters and Labradors, there has been heavy selection for the S gene, because of the disqualification of white markings.

si produces a small amount of white, and is recessive to S.

sp causes the typical particolor pattern of white markings

sw is the most recessive gene in this series, and produces extreme white spotting: an all white dog with dark markings on the head.

As previously mentioned, the dominance of S is not complete. sp combined with S will produce markings indistinguishable from si: a little white ring around the neck, a white head spot and tail tip, and white feet. These markings may reveal the presence of a recessive particolor gene in a presumably solid colored dog. sw, in combination with S or si, can result in atypical particolor patterns. The sw gene is associated with cochlear deafness.

IX. The last gene series is T, the ticking factor. Ticking occurs on white areas which are produced by "S" series genes. Ticking does not occur on white which results from the other white (really cream) producing gene, ce. Paws which were pure white at birth, at three months will be partly filled in, and at maturity may be a roan due to the ticking gene. This gene is rarely if ever seen in Shih Tzu
 Arden_Farms
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7/16/2008 3:25:53 PM reply with quote send message to Arden_Farms Object to Post

GENE SUMMARY

"K" Series: Distribution of dark pigment

Phenotype
K =(Solid Black)
Genotype
K K
K kbr
K k

Phenotype
kbr =(Brindle)
Genotype
kbr kbr
kbr k

Phenotype
k =(any other)
Genotype
k k


"A" Series: Pattern of dark Pigment

Phenotype
Aw =("Wild"wink ;)
Genotypes
AwAw
Aay
Aat

Phenotype
ay = (Sable)
Genotypes
ay ay
ay at

Phenotype
at = (Black & tan)
Genotype
at at

Phenotype
a = (Solid black
Genotype
a a


"B" Series: Type of Dark
Pigment: Black or Liver

Phenotype
B =(Black pigment)
Genotypes
BB
Bb

Phenoype
b =(Brown pigment)
Genotype
bb

"C" Series: Depth of Light Hair Color

Phenotype
Full DEEP color(Red)
Genotype
CC

Phenotype
Full color(Gold)
Genotypes
Ccch

Phenotype
Cream to light gold
Genotypes
cch cch
Cce

Phenotype
Pale cream to white
Genotypes
cch ce

Phenotype
White to albino
Genotype
cece


"D" Series: Blue Dilution(Coat, Nose, Eyes)

Phenotype
D = (Dark)
Genotypes
DD
Dd

Phenotype
d =(Dilute)
Genotype
dd


"E" Series: Production of Dark Pigment
Phenotype
Em = Dark pigment with mask
Genotypes
Em Em
EmE
Eme

Phenotype
E = Dark pigment no mask
Genotypes
E E
Ee

Phenotype
No dark pigment
Genotype
ee



("S" Series: White Spotting, "G" Series: Greying With Maturity and "T" Series: Dark Ticking On "S" White Ground have been left out for lack of relevency)



 Arden_Farms
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7/16/2008 4:42:39 PM reply with quote send message to Arden_Farms Object to Post

btw- the above information was primarily taken from Lhasa Apso coat information as shih tzu information was limited but based on my cross refrences the same basic color genetics apply to both breeds
 Marchen Shih Tzus
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7/16/2008 9:27:42 PM reply with quote send message to Marchen Shih Tzus Object to Post

Just an FYI, when developing the genetics for shih tzus, I did start off leaving out the G locus, but ended up having to add it back in because that is what gives us silvers. The dominant GG causes blacks to silver when they are still young. Gg causes them to gray, but only with maturity, so I did not add any affect to that gene since we obviously will not be changing the color of our dogs on here. gg allows black to stay solid black. So in conclusion, silvers need GG and blacks can have Gg or gg. That is what I found in my research in books, but I do suppose new information could have came out that changed how silvers acquire their color. Silvers can only be silvers if they have black noses. They are blues if they have a blue nose and a blue sheen to their hair.
 Arden_Farms
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7/16/2008 11:02:46 PM reply with quote send message to Arden_Farms Object to Post

Well I debated the G simply because i thought the "age" factor might complicate things... althought for the sake of the game it could be intellectually modifide for the same purpose of simply designating "mature" color from the on set

tommorow when it's not so late i'll add the information if you'd like... or if anyone else would like to.. either way

happy :)
 Marchen Shih Tzus
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7/16/2008 11:07:52 PM reply with quote send message to Marchen Shih Tzus Object to Post

No what I am saying is I didn't consider the maturing greying factor. However, in shih tzus the GG changes blacks to silver as early as 6 weeks. So I considered those dogs silver. The ones with the Gg gradual greying factor, I considered them the color they were born with, not after greying. So that is already included in the genetic locus I suggested in the other discussion.
 gaylanstudio
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10/8/2020 11:56:51 PM reply with quote send message to gaylanstudio Object to Post

this post has been edited 1 time(s)

Ok, stumbled across this while researching your problem. I haven't had a chance to analyze it but you can have a look at it and see what you think.

(I found it through a Google search then posted a "comment" to see if it would bring it back to the current forum.)

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Last edited by gaylanstudio on 10/9/2020 12:02:07 AM

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