- Anatolian Shepherd Breeding Selection Criteria
The Two Most Important Breeding Selection Criteria
For a serious and responsible breeder of Anatolian Shepherd Guardian Dogs, the
two most important breeding selection criteria are proven livestock working
ability and superior flock-guardian temperament. Anatolian Shepherds without
both livestock working ability and superior flock-guardian temperament are
Anatolians in name only and should not be considered for use in any responsible
breeding program.
Superior Flock Guardian Ability Unifies Anatolian Shepherds
Anatolian Shepherds (i.e. Turkish Shepherds' Dogs) have existed in Turkey for
more than a millennium as superior working flock-guardians possessing a wide
range of diversity in both structure and color. The factor which unifies these
"Turkish Shepherds' Dogs" is their uniquely superior flock-guardian ability.
Breed for Proven Superior Genetic Health and Superior Overall Conformation
After eliminating all Anatolians except for those with proven livestock working
ability and superior flock guardian temperament, the serious and responsible
Anatolian breeder's next set of criteria will include only those Anatolian
Shepherds with proven superior genetic health and superior overall conformation.
Over time, placing conformation and genetic health above working ability and
temperament in the breeding selection criteria will change the essential nature
of this amazing breed and will result in Anatolians being just another breed of
large, beautiful, and potentially dangerous pets without any real working
ability.
Color Isn't a Serious Breeding Consideration
In breeding Anatolian Shepherd Guardian Dogs, color should never be a serious
consideration in the breeding selection process.
Dog Color Genetics as an Introduction to Dog Genetics
Color genetics, however, is an interesting and relatively easy first step into
more complex aspects of dog genetics. In addition, there have been some
impressive advances recently in our understanding of mammalian color genetics,
including dog color genetics. The colors expressed in each dog's coat are
unambiguously stamped into the genetic code found in that dog's chromosomes.
This article's goal is to provide a general overview of coat color genetics in
dogs and to highlight coat color genetics in the Anatolian Shepherd Guardian
Dog.
- Brief Historical Background in the Development of Dog Genetics
Clarence C. Little, Sc.D.
Clarence C. Little, Sc.D., provided most of the published information regarding
the genetic basis of coat color in dogs based on older research in classical
genetics. He wrote The Inheritance of Coat Color in Dogs, published in 1957.
Dr. Little worked in and later owned the 20 -100 dog private kennel founded by
his father. For sixteen years Dr. Little performed experiments in breeding for
coat color at the Jackson Laboratory, which maintained some 200-220 dogs of
28 breeds and produced over 4,100 puppies.
Roy Robinson
More recent dog coat color information using classical genetics was provided by
Roy Robinson in his book, Genetics for Dog Breeders
(2nd ed.), 1990.
Molecular Genetics
Our understanding of dog coat color genetics is being greatly expanded by the
advances made in molecular genetics. Molecular genetic research in mouse coat
color has been quite extensive and since coat color appears to be highly
conserved across mammals, much of the information obtained regarding mouse
coat color can be applied directly to dog coat color genetics. Dog coat color
genetic models formulated from information obtained using molecular genetics
research have in some cases clarified and in other cases contradicted the
classical genetics models formulated by C.C. Little.
- General Genetic Information
DNA and Chromosomes
DNA is found in the cells of most living things. DNA consists of strands of
material called chromosomes which are composed from a series of sequences of
four chemicals. Chromosomes are arranged in pairs. Each member of a pair has
the same basic structure except for the fine details.
Loci (Locus)
Along each chromosome in a pair are corresponding sections called loci (plural)
or locus (singular). Each locus of each chromosome relates to some structure
or function of the living entity. Since chromosomes are paired, for each locus
on one chromosome there is a corresponding locus on the other chromosome of that
chromosome pair.
Genes and Allelles
A gene consists of a specific sequence of the chemicals occupying a locus. The
members of the set of genes that could possibly occupy a specific locus are
called alleles of that locus; alleles are all alternate gene possibilities
found at identical loci on the chromosomes.
Only Two Allelic Spaces per Gene Locus
Some gene loci have only two possible allelic choices, essentially resulting in
either an "either/or" outcome or a blending of the two possible allelic
instructions, depending on the dominance relationship of each allele. Other
gene loci have a larger number of possible allelic choices. However, no matter
how many different allelic choices are possible at one locus, only two allelic
spaces are available to be filled per locus (one allele on each chromosome).
The outcome of the interaction between these two alleles results in the gene's
phenotypic (or outward) expression.
Genes Code for Two Different Outcomes
It is important to remember that genes code for two different outcomes. While
one type of gene codes for the structure of a particular protein, another type
dictates when and where associated genes are turned on or off.
Melanin - A Skin Pigment in the Hair Affecting Coat Color
Coat color is affected by pigment in the hair. The biosynthetic pathways
involved in the synthesis of pigments, and the genes involved in the development
of the pigment forming cells (melanocytes), the hair follicle, and the hair
shaft, appear to be very similar in most species. Mammalian pigmentation is
due primarily to the presence of melanin, a skin pigment.
Two Types of Mammalian Hair Pigment - Eumelanin and Phaeomelanin
There are two types of pigment in mammalian hair, eumelanin, a black-brown
pigment, and phaeomelanin, a yellow-red pigment. These two pigments are both
forms of melanin synthesized by the melanocytes. Eumelanin is dark (black or
brown) and varies somewhat in color due to variations in the protein that forms
the framework of the pigment granule. The base form of eumelanin is black.
The brown form is often called liver in dogs. Pheomelanin is light (yellow,
tan, or reddish) and varies from pale cream through shades of yellow, tan and
red to mahogany (as in the Irish Setter). Both melanins are made by a similar
process and the first few steps in their synthesis are identical. Mutations
that affect these identical steps affect both melanins while mutations that
affect steps after their synthesis pathways diverge will affect only one melanin
or the other.
The starting material in melanin synthesis is the colorless amino acid tyrosine.
Tyrosinase, an enzyme by some believed to be encoded from the "C" Locus (The
Albino Locus), converts tyrosine to DOPAquinone, which is also colorless.
Phaeomelanin is made from DOPAquinone by enzymes that attach the amino acid
cysteine to the DOPAquinone and then polymerize the resulting compounds into
masses with a color from yellow through red. Eumelanin is made with the same
initial steps. However, the DOPAquinone is converted to DOPAchrome, which is
converted to complex quinone compounds by the enzyme tyrosinase related
protein I (TYRP1, produced at the B Locus by the brown gene), either directly
or after an intermediate step with another enzyme, DOPAchrome tautomerase (DCT,
believed to be produced by one of the dog dilution genes). The quinones are
then polymerized into eumelanin.
Melanocytes (From Neural Crest Cells) Synthesize Melanin
Melanin is synthesized in specialized cells called melanocytes, which live in
hair follicles. Melanocytes originated from the neural crest cells located on
the dorsal mid-line during the early embryonic stage of development. The neural
crest cells have genetic instructions to become a variety of different organs
and tissues. If the neural crest cells directed to become melanocytes
misinterpreted their instructions or mutated and received the wrong instructions,
they might do some new task or perhaps do nothing, creating an animal with
partial or no pigmentation in the hair or skin. Therefore, some melanocytes
contain skin pigment while others don't. Where there is no skin pigment, white
hairs will be produced.
The melanocytes synthesize melanin, form it into granules, and deposit it into
the hair shaft. Color variation of the hair can occur either from alterations
in its synthesis or variation in the deposition of the pigment. The color of
the pigment granule is dependent on the type and amount of pigment (melanin) in
it. The hair shaft can have greater or lesser amounts of granules deposited in
it, producing variation in shade and intensity of color. The color and density
of pigment granules can vary between individual hairs as well as varying in
locations along the length of the hair shaft in a single hair.
Coat Color Gene Control Overview
Coat color is affected by genes which dictate the size, shape, position, number,
and arrangement of the melanin granule in the hair (i.e. a denser granule
arrangement lightens hair). Genes also affect the type of melanin the coat
hairs contain. The structure and texture of the hair and the intracellular
environment also affect coat color. Further, the same genes may result in
very different effects on different types and lengths of coat.
In general, genes that control dog coat color:
- Produce either black-brown or yellow-red pigment in the coat hairs;
- Alter the base color pigments to produce a modified base color;
- Dictate the assigned body locations for different colors;
- Control specific color placement, including variations, on individual hairs; and
- Fail to code for color pigment, resulting in the production of white hairs.
- Gene Loci in Dogs
- Pigment pattern regulation
Three groups of genes regulate the pattern of pigment in individual
hairs and across the body.
- The "A" and "E" Loci control pigment distribution patterns (also,
perhaps, the "Ma" locus). The "A" (Agouti) Locus, which blocks
black, and the "E: (Extension Locus), which controls the extent
of the extension of black across the coat, dictate the distribution
pattern of eumelanin (black/brown) and phaeomelanin (red/yellowo)
pigment in the coat. The gene controlling brindle (Kbr) and the gene
controlling black mask (Em) might also be included as pigment
distribution pattern loci. These gene loci control pigment
distribution patterns without contontrolling the actual color
of the pigment.
- The "B," "C," "D," "G," and "M" loci modify color by
diluting colors The dilution loci are a variety of less well
understood genes which modify the color of the eumelanin and
phaeomelanin pigment. Some of these loci are "B" (Brown) Locus, "C"
(Albino) Locus, "D" (Blue Dilution) Locus, "G" (Gray) Locus, and "M"
(Merle) Locus. The "C" Locus is the only gene location that fully
affects the synthesis of both melanins. The other genes primarily
affect eumelanin synthesis. Although no gene has as yet been
identified that affects primarily phaeomelanin synthesis, an
intensifier loci and the loci for "fawn" are possibilities. All
of the dilution loci interact in what seems to be a cumulative
manner (as the total number of dilute genes increases the coat
appears progressively lighter). Dilution loci control the color
of the eumelanin and phaeomelanin pigments but not their
distribution patterns.
- The "S" and "T" loci control the placement of white areas
on the dog's body. More specifically, The "S" (White Spotting)
Locus and the "T" (Ticking) Locus (which actually may be an
allele of the "S" locus) control the presence, location and size of
white (unpigmented) areas.
- The "A" Gene Locus (The Agouti Series)
controls the degree and placement of black and yellow on individual
hairs and body regions by inhibiting eumelanin (black pigment)
production. In general, more yellow is dominant over more black.
- The "A" (Agouti) Locus Can Block Black by producing the Agouti Protein
The "A" locus (Agouti Series) is the most important color locus in dogs
and contains between four to six different alleles. The Agouti (A) gene
was recently cloned. In mice, this gene has a large number of alleles
whose synthesis is under complex regulation. The basic function
of Agouti locus genes is to code for the production of a small
signaling protein, the Agouti Protein (AP), to be secreted from
dermal papilla cells in the hair follicle. This protein attaches to
the MC1R receptor on the melanocytes, blocking the Melanocyte Stimulating
Hormone (MSH) from binding on the MC1-R receptor and causing the melanocytes to
produce a low level of tyrosinase. Low tyrosinase levels result in
phaeomelanin (yellow/red) production rather than eumelanin production.
Therefore, when the Agouti gene is present,
melanocytes produce mostly phaeomelanin and much of the coat is some
shade varying between dark red through pale yellow. The agouti pattern
is a mostly red/yellow pattern that supercedes the dog's underlying
genetically directed solid black color. As a rule, agouti genes don't
alter the dog's skin color since skin melanocytes aren't regulated by
MSH and don't use the MC1R/agouti system.
- Two promoters are associated with the wild type agouti gene.
- Two promoters are generally associated with the "wild type" version of
the agouti gene. One promoter (the cycling promoter) produces a
banded hair with a black tip and yellow middle over the entire body.
The other promoter (the ventral promoter) directs that there be
only yellow color in the hair but only in the hair on the belly. So
the animal will have black banded hair on the dorsal surface and paler
yellow hair on the ventral surface.
- The action of these two promoters can be interrupted independently.
If only the action of ventral promoter is disrupted, the dog's hair will
be banded over its entire body (solid agouti). If only the action of the
cycling promoter is disrupted, the dog's back will be black and its belly
will be yellow (which produces the black and tan.)
- If both promoters are disrupted or some other alteration inactivates the
agouti protein, the animal appears solid black.
- Also, a promoter mutation can occur that causes the yellow to be expressed
over most of the body surface.
- AS - Dominant Black Allele (It was very
recently proven that dominant black isn't in A locus or in E locus, but
somewhere else.
)
- The traditional belief is that domestic dogs have a dominant black allele,
AS, at the "A" locus. No other mammal has dominant black at the "A" locus
and the dominance hierarchy in general moves from less dark pigment to
more dark pigment as the alleles become increasingly recessive. Dominant
Black at the "A" locus would violate that trend. As a rule, more yellow
is dominant to more black.
- Dominant Black was placed in the Agouti series by Little. However, all
other mammals have Dominant Black in the Extension "E" Series (see below),
rather than in the Agouti series. It is unlikely that dominant black is
actually in the Agouti series in dogs for these and other more empirical
reasons relating to the genetic mechanism at this locus. Therefore,
until recently (2003)it had been considered that Dominant Black should be
placed under "ED," Dominant Black, in the "E," Extension Series.
- When dominant black is present, the dog is able to produce only
eumelanin pigment.
- This allelic assignment, AS as "Dominant Black," was recently
reevaluated and is incorrect. It was very
(2003) recently proven that dominant black isn't in the A gene locus
or in the E gene locus, but somewhere else.
- Note that in the "A" series some authors use the AS designation for the
Sable allele instead of using AS incorrectly for Dominant Black
allele (Also see "E" series for Dominant Black). In this document, the
Sable allele is designated AY.
- It has been speculated that the decreasing order of dominance of the
alleles at this locus are AY, asa, at aw, and aa. (The dominance order
of these genes has not yet been verified with certainty.) The last
allelic pair, recessive black (aa), is extremely rare but has been
observed in German Shepherds and perhaps Shetland Sheepdogs. Sufficient
coat color information on Anatolian Shepherds has not been collected
and examined to eliminate the presence of recessive black (aa) in
Anatolians.
- AY - Sable allele produces fawn (yellow/red) with variable amounts of black.
- In Anatolian Shepherds, the almost universally found allele of the "A" series
is the sable allele, AY. Anatolian Shepherd owners use the term "fawn"
rather than sable to describe this color. The AY , or sable, allele produces
fawn colored dogs from phaeomelanin (yellow/red) color pigment because the
sable allele inhibits eumelanin (black). Depending on other genetic color
factors, the sable allele can result in a dog with a color range anywhere
from a pale biscuit through shades of yellow to a rich red. The sable allele
can produce varying amounts of black hair ranging from solid black to black
tipped and varying in body placement. Generally, a sable Anatolian Shepherd
is mostly yellow/red (phaeomelanin) with some black tipped hairs. Both black
and yellow/red pigment can be found on the same hair. Even if there is no
black in the dog's coat, a sable dog's whiskers (the stiff vibrissae)
originating from pigmented skin are black. The sable allele also permits
the production of some longer black (especially on the dorsal surface)
hairs (which can be called sailing) on the fawn background. This allele
also permits a black mask and ears and possibly brindle.
- Phaeomelanin is apparently the "default" pigment when the production
of black pigment is suppressed. Therefore, without other gene directed
enzymatic and regulatory activity, a dog's coat will become some shade
of yellow. Pigment modifying factors can result in yellow phaeomelanin
shades anywhere from light cream to dark red color variants. For
phaeomelanin production, the enzyme tyrosinase converts tyrosine into
a compound named DOPAquinone. The genes directing the final steps
to phaeomelanin production have yet to be clearly delineated.
- aw - "Wolf-color" allele (or ag - Wolf-gray allele) creates a
wolf colored coat.
- This allele's effect is most clearly observed in the coats of Norwegian
Elkhounds. In the "A" series of most mammals, the agouti (a+) allele is
generally considered as the wild-type allele. However, in dogs (aw)
[sometimes designated (ag)] perhaps best serves the function of the
wild-type allele. Currently, we do not know how similar or different
the a+ alleles and the aw alleles are.
- The aw allele varies from the AY (sable) allele in two notable ways.
The yellow/red is replaced by a pale cream to pale gray color and the
hairs are banded with several bands of alternating light and black
pigment rather than the scattered black tipped hairs seen in sable.
- asa asa - "Saddle tan" allele places a black "saddle" on a tan dog's back
- This color is seen in many terrier breeds having a black "saddle" on
their back and extensive tan on their legs and head.
- Some believe that, rather than being a separate gene, the saddle
tan allele is a variation of the black and tan allele that produces a
small amount of black across the back due to the effect of modifiers.
- at at - Black and Tan allele places "tan points" on the dog's body
- "Tan points," composed of hair with only yellow/red (phaeomelanin) pigment,
are placed on the cheeks of the muzzle, the chest, the end of the legs,
around the anus under the tail, and on the eyebrows.
- Only black (eumelanin) pigment is found in hair in all other body regions.
- aa - Recessive Black allele occurs if the Agouti Protein can't be
made, resulting in only black pigment production.
- The recessive black allele (aa) is a mutation that results in the loss
of ability to synthesize the Agouti Protein (AP), which inhibits the
production of black pigment. Without the inhibition of black pigment
production, only eumelanin (black pigment) is produced by the
melanocytes.
- This same type of mutation results in "recessive black" (aa) in horses,
mice, fox, and many other mammals that have a solid black color variant
originating from the "A" Series.
- Since black is the most recessive color in the "A" series in other
mammals, it seems reasonable to believe that recessive black in dogs
is also in the "A" Series and is also the most recessive color.
Therefore, it is currently believed that recessive black is produced
by "aa" at the Agouti Locus.
- The "B" Gene Locus (Brown Series) produces either black or
brown eumelanin
- The Brown Locus affects only eumelanin (affects only black/brown,
not red/yellow). In mice, the Brown Locus, codes for an enzyme, tyrosinase-related
protein 1 (TYRP1), which catalyzes the final step in eumelanin production,
changing the final intermediate brown pigment (dihydroxyindole)
to black pigment. It is believed that this gene, using the same mechanism, is also
responsible for the expression of brown in dogs.
- "B" - Dominant B (Black) - The dominant gene (B) directs the color
of eumelanin produced to be black. This direction includes the
black color seen on the body, masks, ears, brindle stripes, etc.
Pigmented skin areas (like the nose leather, lips, and eye rims)
are black.
- "bb" - Recessive "bb" (Brown) - The recessive gene (bb) directs the
color of eumelanin produced to be a chocolate brown but does
not take the final step in eumelanin production of changing brown
to black. Phaeomelanin (yellow/red) isn't affected. The pigment
granules produced by "bb" are smaller, rounder in shape, and appear
lighter than pigment granules in "B" dogs. Pigmented skin areas
(like the nose leather, lips and eye rims) are brown, not black.
Also, the iris of the eye is lightened. Some "liver" and "chocolate"
colored dogs, especially in the sporting breeds, carry the "bb" gene.
This is also the gene responsible for "reds" in Dobermans (bb) and
perhaps the bronze Newfoundlands.
In the "bb" recessive brown Anatolian Shepherd with an AY sable (fawn)
coat (the most commonly seen Anatolian coat color), the coat will be
shaded with brown rather than with black. The "bb" will perhaps result
in a fawn that has an orangey cast with light brown eyes, brown nose
leather, and brown eye rims. The only Anatolian Shepherd I have
personally seen that I believe carried the "bb" recessive brown (light
brown eyes, brown nose leather, and brown eye rims) was a pale
white-cream colored dog called Blue. Blue's eyes remained blue
until he was four months old and gradually became a yellowish brown
color.
Note:
- Some shades of liver (brown), expressed through "bb" eumelanin
(black/brown) pigment, overlap some shades of tan (yellow/red), a
phaeomelanin pigment.
- The "B" locus acts only on eumelanin (black) pigment.
- The "C" locus has the strongest effect on phaeomelanin (red/yellow)
pigment.
- The "D" locus affects both phaeomelanin (red/yellow) and
eumelanin (black) pigment.
- The "C" Gene Locus (Albino Series): a dilution loci which
selects for color across a range from full color through no color. More
color is incompletely dominant over less color. It is the only gene
location that fully affects the synthesis of both melanins.
- Tyrosinase is the enzyme responsible for the initial step in
melanin synthesis.
Both types of melanin, eumelanin and phaeomelanin, depend on the
enzyme tyrosinase for their production. In mice, the chinchilla (cch) allele
produces a defective tyrosinase which synthesizes abnormally low quantities
of melanin. The melanin synthesized tends to be the dark eumelanin.
Although the degree of lightening varies by species, the eyes and nose
generally remain dark.
- True albinos produce no melanin based pigment
Current thought is that a true albino, whose melanocytes produce
no melanin- based pigments, results from a complete malfunction in
tyrosinase production. While CC or Cc dogs' coats have full color,
as directed by their other color genes, albino (cc) dogs' coats
are homozygous for a recessive mutant allele. Albinos, who have
no pigment, are either very rare or non-existent in dogs.
- The following potential alleles have been suggested for the "C"
Series in dogs:
- "C" - Full color - the dominant allele in the "C" series.
This allele allows for the expression of full color. "C" is the
only allele of this series which is present in most breeds and
is probably the structural gene for tyrosinase.
- "cch" - chinchilla silvering. It is incompletely dominant.
Chinchilla imparts a lightened, flat tone to non-black pigments
without greatly affecting black. (In dogs, the chinchilla gene
lightens yellow, tan or reddish phaeomelanin to cream but has
little noticeable effect on the dark eumelanin, so it affects
phaeomelanin more strongly than eumelanin and brown or dilute
eumelanin more strongly than black eumelanin, to the point that
it has little effect on solid black dogs. Under it's influence,
brown becomes milk chocolate, blue becomes silver, and red
phaeomelanin lightens toward cream.)
The "chinchilla" gene may be a factor affecting the coat color
of some of our light Anatolian Shepherds. Those breeders with
very light colored dogs may wish to consider this possibility
and help determine how prevalent, if present at all, this gene
is in the Anatolian Shepherd.
NOTE! Recent genetic information indicates that although a
chinchilla-like mutation occurs in dogs, tyrosinase activity
hasn't been shown to be connected. Therefore, some other factor
may be at play and the dog chinchilla allele may not belong in
this series. Also, there may be more than one form of the
chinchilla gene; for instance, rabbits are thought to have
three different chinchilla alleles.
- "ce" - (extreme dilution) represents an extreme silvering,
approaching white. If this gene exists, it might be responsible
for the lightest colored Anatolian Shepherds. Some white dog
breeds may be produced by this gene where the white results from
the extreme dilution of yellow/red (phaeomelanin). For example,
the West Highland White Terrier may be (cece)(ee). This
gene (ce) does not appear to lighten eyes in dogs.
- "ch" - Himalyan - isn't known to occur in dogs but is an
interesting allele in the C series. When homozygous (chch),
the formation of eumelanin becomes dependent on skin temperature.
A genetically solid black animal has reduced black on extremities
(seal brown) and an almost white coat on the body.
- "cb" - blue-eyed albino - Blue-eyed albino and true
pink-eyed albino are very rare in any dog breed, if present at all.
However, it may be responsible for the pink skinned, blue eyed
white Doberman.
- "c" - true pink-eyed albino - not documented as occurring
in dogs but in other mammals it stops melanin formation completely,
including skin, coat, and eyes, resulting in a pink eyed white animal.
"c" directs production of a form of tyrosinase that doesn't function
properly in melanin formation. There can be a number of different
forms of "c" since there are a number of ways for something to not
work properly.
Note:
- The "B" locus acts only on eumelanin (black) pigment.
- The "C" locus has the strongest effect on phaeomelanin (red/yellow)
pigment.
- The "D" locus affects both phaeomelanin (red/yellow) and
eumelanin (black) pigment.
- The "D" Gene Locus (The Blue Dilution Series): a
dilution loci that controls the dilution of eumelanin and phaeomelanin.
- "D" - wild type; normal color - the dominant allele codes for full color
pigmentation.
The full color allele at the "D" gene locus is called "D."
- "dd" - blue dilute; the recessive allelic pair codes for dilution of black
and yellow/red pigment. In some breeds "dd" has been associated with skin
problems.
In general, "dd" acting on phaeomelanin coat color seems limited to breeds
in which color is of little importance (as is true in Anatolian Shepherds).
Phaeomelanin responds by producing a flattened or dulled coat color.
The recessive allelic pair, "dd," dilutes eumelanin (black) pigment into
a gray-black or bluish gray and also lightens and dulls phaeomelanin
(reds and yellows) to a silvery or flat shade of the yellow through red color.
Pigmented skin will also be a lighter blue or gray color and the irises
may be a lighter brown or gold.
Although rare in Anatolians, "dd" has been observed. It is most easily
noticed in "blue masked" (rather than black masked) Anatolians. Black dogs
with the recessive "dd" are sometimes called "Maltese blue." A pure liver
dog (chocolate brown - bb) that also carries "dd" results in the silvery
blue color of Weimeraners or isabella Dobermans (sometimes called fawn,
in Dobermans, and also lilac colored in other breeds). In Anatolian Shepherds
and other dog breeds, fawn refers to the yellow and black sable coat color
produced by the Ay allele.
Some believe that the dilute color produced is from the same genetic origin
(bbdd) that produces color in the dilute trait in mice. It is a mutation
of myosin V, a motor protein that's involved in transport of the pigment
granules in the melanocytes. The pigment granules are normal but
inefficiently deposited.
However, others believe that the dog dilute trait isn't caused by this
mechanism. Instead, they believe that this color is caused by a mechanism
similar to the "slaty" mutation in mice, which involves a mutation of DOPA
chrome tautomerase (DCT). This DCT mutation in mice results in a paler,
grayish coat.
Note:
- The "B" locus acts only on eumelanin (black) pigment.
- The "C" locus has the strongest effect on phaeomelanin (red/yellow)
pigment.
- The "D" locus affects both phaeomelanin (red/yellow) and
eumelanin (black) pigment.
- The "E" Gene Locus(Extension Series): Controls the
distribution pattern of pigment (the degree and placement of black and yellow
on individual hairs and body regions) by controlling the extension of black
pigment across body regions of the coat.
- The Extension of Black Color Across the Coat
The "E" Locus (Extension Series) has been cloned and sequenced. It encodes
for production of the melanocyte stimulating hormone receptor, or
melanocortin 1 receptor (MC1R). MC1R is a protein attached to the surface
of melanocytes that controls the amount of tyrosinase melanocytes produce.
A small protein in the blood, alpha melanocyte stimulating hormone (MSH),
binds to the MC1R receptor and passes a signal to regulatory factors inside
the cell, causing the melanocyte to increase the level of tyrosinase.
Tyrosinase is the limiting enzyme involved in melanin synthesis and when
found at high levels eumelanin (black/brown) is produced. Low tyrosinase
levels result in phaeomelanin (yellow/red) production. Because MSH is
always present in relatively high levels in dogs, all dogs would be solid
black without the influence of other coat color genes.
This two step mechanism to produce solid black may be related to the fact that
in many wild animals melanocortin levels vary seasonally, causing their coat
colors to vary seasonally. When coat color is linked to seasonally
variable melanocortin levels, you may have animals with a white winter coat
and a dark summer coat. Dogs, however, maintain fairly constant (and high)
levels of MSH so don't exhibit seasonal color changes.
The "E" Locus (Extension Series) has the following alleles:
- "ED" - Dominant Black: It was believed that Dominant black results from a
mutation of the MC1-R protein that causes the melanocytes to believe they are
receiving a signal even though they aren't. With dominant black, only eumelanin is
synthesized, resulting in a black dog (if eumelanin dilution modifiers aren't
present). This mutation was referred to as dominant black because it was
believed to be the dominant allele at the "E" Locus. However,
it was very recently proven that dominant black isn't in either the A gene locus
or in the E gene locus, but somewhere else.
It's important to remember, however, that
not all black dogs are dominant black. Some black dogs are produced by
recessive black, the (aa) alleles found at the A Locus (the Agouti Series).
- "Em" - Black Mask and Ears is believed to be the dominant
allele in this series.
"Em" is a gene which attempts to produce a black mask and ears, but
restrict the rest of the coat to the yellow-red range. Whichever gene causes
black mask, most Anatolian Shepherds have it.
- "E" - Wild Type: capable of producing both pigments. This allele
allows the melanocytes to respond to the signals from other cells and tissues
and is the gene for extending black pigment over the whole body. Under the
influence of other genes the expression of black may be suppressed.
- "ee" - Recessive Red/Yellow, the non-extension gene: This allele
is a mutation which codes for a total loss of function in homozygous (ee)
dogs. "ee" produces a defective MC1-R protein that can't pass on the signal
from MSH, so the melanocytes synthesize only phaeomelanin. Because it is
recessive to the others, the gene pair has to be "ee" for it to have any effect,
but in that case, it produces clear yellows or reds with no black hairs at all.
Genetic testing on dogs has shown that pure red/yellow, cream, and white can be
produced by genetically "ee" dogs. This gene may exist in Anatolians. It may
be the gene that produces dogs without masks.
- "Ebr" - Brindle:
It is now known that brindle isn't at the E gene locus, but somewhere else. Brindle
is one of the alleles located on the K locus. The three K locus alleles are: KB (dominant black),
kbr (brindle) and ky (non-solid black which allows the A locus to be expressed).
KB is the most dominant and ky is the most recessive. kbr is recessive to KB but
dominant to ky. It is entirely dominated by KB (so just one KB allele will stop
brindle from being expressed), but is dominant over ky, so a brindle dog can have
the genotype kbrkbr or kbrky.
- The "G" Gene Locus (Gray Series): Controls the
dilution of black to white in individual hairs.
Although the dog trait for gray doesn't closely match any mouse traits for gray,
it is similar to a mutation of the mouse TYRP1 gene. This mutation in mice
causes the enzyme to produce a toxic intermediate that eventually kills the
melanocyte. Young melanocytes produce dark, fully pigmented hair tips but
as the melanocytes slowly die the hair color fades until it is nearly white at
its base. When the hair falls out, melanocyte stem cells in the hair follicle
produce new melanocytes and the cycle repeats itself.
Little recognized only two alleles for gray:
- "G" - Dominant "G" Allele - Graying: graying occurs as the animal ages.
"G" or "Gg" animals have eumelanic (black)areas of the coat that
lighten slowly with age to blue-gray in a manner similar to premature
graying in humans.
- "gg" - Recessive "gg" Allele - Wild Type: no graying is seen
However, this series is almost certainly more complex and should have more
alleles or is a generalized trait that is affected by more than one locus.
For example, another potential graying locus that is seen in Anatolian
Shepherds is the gene that controls graying of the muzzle and over the eyes
of aged dogs with black masks. This locus doesn't affect the dog's skin or
phaeomelanic (yellow) hair. Graying may begin as early as immediately
after birth or be delayed for weeks, months, or years and may reach its most
faded state by the first adult coat or continue throughout the animal's
lifetime.
- The "I" (Intensifier Series) Locus: Controls the synthesis of
phaeomelanin (a red/yellow dilution locus) without changing eumelanin
(black) pigment.
- The speculative "I" gene locus is not well understood. However,
dogs are descended from wolves, which have paler phaeomelanin pigment than
found in many dog breeds. Anatolian Shepherds commonly have very pale
phaeomelanin pigment. Some breeding experiments indicate that the pale
"wild type" phaeomelanin typical of wolves is dominant to the "intensified"
red phaeomelanin common in many modern dog breeds.
- The intensifier locus is a possible gene influencing the synthesis
of phaeomelanin. However, this simple scheme using only three alleles
and one locus may be far too simplistic.
- wild type (pale phaeomelanin)
- Intm - slight intensification (intermediate color)
- int - intensified (red)
- The "K" (Dominant Black Series) Locus: The K locus, also
known as the dominant black gene, consists of three different alleles and
results from a mutation in a Beta-defensin gene
(CBD103). Variations in the K Locus are produced when this gene binds proteins
and other pigment type cells. It impacts many types of colorations. The K locus
is dependent on the E locus. When the E locus genotype is e/e (recessive), the
K locus is not expressed. When the E locus is coded as E/E or E/e, the K locus
is expressed.
- The “KB” Allele: is dominant and identified as "KB," or dominant black.
The dominant black allele is a mutation that reduces or eliminates the
expression of the agouti gene (A locus). Being dominant, only one copy of the
mutation is required to affect the agouti locus. A dog that is KB/KB or KB/n
will be solid black in color.
- The “Kbr” Allele: the "brindling" allele, idenditied as "Kbr," and allows
the A locus to be expressed as brindling of the agouti patterns. (The A locus
represents several different colors, such as fawn/sable, wolf, tricolor,
tan points, or recessive black.) The Kbr allele is recessive to the KB allele,
meaning a KB/Kbr genotype appears black, not brindle. However, Kbr (brindle) is
dominant over the third allele, Ky. At this time (2020), there is no direct test
for the Kbr allele.
- The “Ky” Allele: allows the agouti gene to be expressed without brindling.
When a dog is Ky/Ky at the K locus, it is the A locus that determines the dog's
coat color. The Ky allele is recessive to both KB and Kbr.
- The "M" Gene Locus (Merle Series): Controls the
dilution of the dog's coat in a patchy pattern of normal and dilute color.
Merle is an intermixed or patchy pattern of various light and dark areas in
eumelanic (black)areas of the coat. Merle does not affect phaeomelanin
(red/yellow). Merle has two related patterns:
- harlequin, where an additional merle modifying dominant gene (most
commonly associated with Great Danes) turns the lighter patched areas white.
Harlequin Great Danes continue to produce merles, which indicates that animals
pure for this gene may not exist. It is believed that this gene, when
homozygous, is an embryonic lethal.
- tweed, where another additional merle modifying dominant gene
makes the light areas have different intensities. This gene is seen in
Australian Shepherds
Merle acts only on eumelanin (black pigment), not on phaeomelanin (red/yellow
pigment). Under the influence of the merle gene, a black coat becomes gray
splotched with black and a liver coat becomes dilute red patched with liver.
Liver is black (eumelanin) acted on by "bb," the Brown Series dilution
gene. These patches or splotches are large and clear because they are clonally
derived (a specific black area is populated by melanocytes descended from
one melanoblasts [immature melanocyte] from which the transposon excised
cleanly.
The lighter patches in a merle dog result from either melanocytes containing
transposons in one of the merle alleles or melanocytes from which the transposon
inaccurately excised. The black areas contain melanocytes in which the
transposon excised cleanly enough to restore full gene function. In adult dogs
it is difficult to distinguish sable merles from sables. Merle is clearly
visible at birth but fades with age.
Merle (M) (as well as Spotting [S]) results from genes affecting the
melanocytes' migratory pathways which have provided the "wrong" signal or
which have interpreted the signal incorrectly due to a mutation. Merle
acts as a "minus" modifier for alleles of the "S" Locus (Spotting Series).
Merle is an example of incomplete dominance (a gene
with intermediate expression):
- "MM" - Double Merle alleles produces almost white dogs: These
dogs have more white than is normal for the breed (they are almost all white).
They may also have hearing losses, vision problems, brain defects, and perhaps
infertility, indicating that the merle gene is not solely a pigmentation
gene. If "MM" is present in the presence of a white spotting gene, these
physical problems seem to be far worse.
- "Mm" - This combination results in a dog with the merle pattern
in eumelanic areas: The eyes of an Mm dog can be blue or merled
(brown and blue segments in the eyes).
- "mm" - Normal color - No merling is seen in the dog.
An interesting theory is that merle is a "fragile" gene that easily allows
the merle (M) gene to mutate back into the non-merle (mm) gene. This
"fragility" may be caused by a transposon, which is a small mobile "parasite"
DNA element similar to a virus. Rather than infecting other animals, the
transposon infects the host's offspring.
Much mammalian DNA consists of inactive "dead" (mutated) transposons, which
are found in nearly all animals. Active transposons are a major cause of
mutations. Transposons can move around. When they "jump into" a gene they
can disrupt its function.
The transposon responsible for merle is called "non-replicative," meaning
that when it "jumps out" of a location function may be restored to its host
gene. More often, the transposon excises sloppily and leaves an irreparably
damaged gene behind. If the transposon excises cleanly in a cell that goes
on to become a sperm or ova, offspring conceived from that germ cell will
revert to wild-type.
The coat pattern of merles (Mm) would occur as some
clonal descendants would be from migrating melanocytes which reverted from
(Mm) to (mm) as they migrated to their final location in the skin, producing
black patches, while other clonal descendents from other migrating melanocytes
would have remained (Mm), producing the lighter patches.
This theory also explains why occasionally a double
merle (MM) bred to black can produce a black puppy. When this occurs the
mutation most likely occurred in a germ cell. Of course, this solid black
puppy can also be (Mm) genetically but have such large patches of black that
merling patches are hidden.
- The "Ma" Gene Locus (Black Mask Series): Codes for the presence or
absence of a black mask and ears (a distribution pattern).(Believed to be true in 2000
but not correct!!!)
Em in the "E" gene series actually controls Black Mask. The expression of this
gene is commonly seen in Anatolian Shepherds.
- Em - : produces a black mask and ears. This gene directs the
distribution of eumelanic (black) pigment over the dog's nose and sometimes
the ears, top of the back, chest, tail, and /or feet. The range of distribution
of eumelanic hair varies from only a small amount of darkening at the muzzle
through an extensive spread across the dog's body. It is believed that
this wide variation is caused by several different alleles for black mask,
a number of modifier genes, or both. Black mask is now believed to be
dominant to agouti while white spotting is dominant over black mask. It
is possible for black mask marking not produced by Em to fade or reduce in
size as the puppy ages.
- ma - recessive: no mask is produced - is no longer accepted as a correct allele or locus
- The "P" Gene Locus (Pigment Series): Controls the
density of dark pigment (a dilution loci) without changing red-yellow pigment.
Some have speculated there is a color locus, "P," which acts on the dark
(eumelanin) pigment in such a way that a homozygous recessive expression (pp)
at this locus will greatly reduce the dark pigment of the coat without changing
the red-yellow pigment.
- P - Dominant - full pigment effect
- pp - Recessive - reduces dark (eumelanin) pigment without
changing red/yellow (phaeomelanin) pigment.
However, others believe that modifiers increased and decreased the pigment
intensities for both eumelanin and phaeomelanin.
A third possibility discussed is that the observed effect described here is
from the umbrous polygenes rather than a speculative "P" Gene locus.
- The "R" Gene Locus (Roan Series): Controls a distribution
pattern for intermixed white and colored hairs.
If a pattern of intermixed white and colored hairs occurs throughout the coat,
the coat is called roan. However, if colored areas are in a white
background and contain no white hairs, these colored areas are called ticking
or flecking.
The Roan Series may or may not be a true series. Instead, it may
simply be an allele of the Ticking Series that produces very fine ticking.
Like ticking, roan seems to be dominant over non-roan. Therefore, it might
be best if roan were treated as an allele of the Ticking Series rather than
placed in its own Series.
There are two ways roaning develops. Dark hairs may appear in an initially
white area or white hairs appear in an initially dark area (which may also be
caused by the gray gene).
Two alleles are generally identified in the Roan series.
- "R" - Roan - a dominant gene
- "rr" - Not Roan - recessive
- The "S" Gene Locus (Spotting Series): Controls
a distribution pattern for white by affecting the degree of White Spotting
White spotting in dogs is controlled by genes which alter the migratory
pathways of melanocytes. Melanocytes originate from the neural crest
cells, which are found along the midline of the back early in embryonic
development and which develop into a number of different cell types,
including much of the peripheral nervous system. Most of the connective
tissues, cartilage, and bones are generated from the cranial neural crest
cells, which are found in the embryonic head area.
A reduced number of melanocytes are formed if the number of neural crest
cells is lower than normal because the other, more important, cell locations
are favored over the melanocytes. These immature melanocytes (called
melanoblasts) spread outward from the dorsal midline over the surface of
the animal. Therefore, in mutations that affect the number or migratory pathway
of melanoblasts, melanocytes are most likely to fail to reach areas further
from the dorsal midline (feet, chest, and muzzle), resulting in white spots
at these locations.
In Anatolian Shepherds, the S Locus may be seen in colors ranging
from solid (no white), to Irish Marked (called "Dutch Marked" in Anatolian
Shepherds), to piebald ("pinto" in Anatolian Shepherds), to solid white.
The great variability within each type makes it unclear how many alleles
actually occur at this locus. Modifying genes (see polygenes below)
greatly affect the expression of the spotting gene.
A recessive gene is required to place white on a dog's coat. The recessive
spotting gene alleles, which all code for some degree of white spotting,
exert only incomplete dominance over their more recessive allelic
counterparts. In general, dominance is incomplete, with more color being
dominant over less color.
Besides expressing incomplete dominance, all spotting gene alleles are also
affected by plus and minus modifying polygenes. In general, however,
more color is believed dominant over less color. Because of the great
variability in each of the four spotting gene alleles generally listed,
the actual number of alleles possible at this locus currently can't be
determined with certainty.
The white spotting genes function by providing the "wrong" signal or
interpreting the signal incorrectly. These altered signals affect the
location and extent of white (unpigmented) areas.
The following white spotting alleles, proposed by Little, are arranged in the
descending order of dominance. (However, recent studies suggest that the
arrangement by Little is overly simplistic and that there are at least three
major genes (loci) needed to explain white spotting inheritance.)
- S - Dominant "S" (Self) Allele - Produces complete pigmentation.
This allele is dominant and the no-spotting gene (doesn't allow spotting).
An "SS" (solid-solid) Anatolian Shepherd may be completely solid
or may have very minor white markings, such as a white spot on the chest,
a white tail tip, or white on the toes. This is the normal gene in breeds
without white markings.
- si- Irish spotting Allele (called Dutch Marked in
Anatolian Shepherds)- Irish spotting creates a white collar and blaze
with some white on the belly, legs and chest and white does not cross the
back between the withers and the tail but may be on the back of the neck.
This allele may be additive as dogs believed to be homozygous for Irish
Spotting have irregular white patches on their bodies. The number and size
of these patches is extremely variable.
- sp - Piebald spotting Allele (Pinto in Anatolian
Shepherds) - codes for colored patches on a white background. The piebald
allele results in well defined areas of colored and white hair. A piebald
(pinto) has more than 50% of its body covered with white. The white often
will cross the back and creates a pattern that appears as large colored spots
on a white background.
- sw - Extreme White Piebald Allele (either Pinto or White in
Anatolian Shepherds)- creates a few small colored spots on a white background.
Coat color ranges from colored heads and a few colored spots on the body,
especially near the tail, through dogs with color only around the eye or ear.
Also, all white animals may be produced in some dog breeds, including
Anatolian Shepherds.
The Robison White Spotting Scale - An alternate white spotting theory - Roy
Robison created a scale with ten types of spotting to help clarify the degree
of spotting in individual dogs.
White Spotting in horses has been extensively studied and is known to be
caused by a variety of different gene loci rather than just one locus as proposed
in dogs. Instead of just the one gene locus proposed by Little and later
by Robison (above) for dogs, perhaps dogs possess several such white spotting
gene loci.
In more recent studies in Landseer dogs, this "one locus" view was
suggested to be over-simplistic. These studies also speculated that at least
three major genes are needed to explain the observed inheritance of
white-spotting in dogs. For instance, there are white dogs with completely
colored heads and solid colored dogs with half or all white heads. This kind
of obvious deviation in head marking indicates that there is at least another
gene affecting head markings.
Because of our current, incomplete understanding
of the genetic mechanism controlling white spotting, it is evident that
further genetic research is required to more fully understand the genetic
control mechanisms which produce white spotting.
- The "T" Gene Locus (Ticking Series): Controls
the placement of black hairs in white areas of the coat
Ticking appears as small spots of uniform color occurring in otherwise white
areas of the coat. The term ticking does not include either the much larger
sized true spots or roan, which is a random mixture of individual white
and colored hairs (or perhaps roan is just and extreme expression of "T").
The color of the colored hair in the ticking is the color that the coat
would have been in that area if the white spotting genes were not present.
A sable (fawn in Anatolian Shepherds), especially one with very light
phaeomelanin, may not have obvious ticking since the contrast between the
tan and white may be faint. However, a close examination may reveal tan
spots on the legs.
Ticking is also more difficult to identify on long haired dogs. Ticking has
been observed in Anatolian Shepherds but since light fawn (sable) is common,
this genetic trait may frequently be overlooked without careful examination,
which often reveals the flecks on the legs.
Ticking has two identified alleles. However, some believe that more than two
alleles may be involved and that ticking is greatly affected by genes which
modify the size, shape, and density of tick marks.
- "T" - Ticking (an incompletely dominant gene)
- "tt" - wild type with lack of ticking (a recessive gene
leaving the solid white spots free of colored hair)
- Polygenes
- General Information regarding Polygenes
- Polygenes are a set of gene alleles scattered over a number of different
loci (rather than found only at one gene locus), and all working together to
create a specific characteristic in the animal.
- Natural selection is more efficient and evolutionary changes can occur more
rapidly when one gene locus controls a characteristic.
- A species is more likely to survive extreme environmental changes if
that species is able to adapt by modifying its major characteristics rapidly.
Therefore, essential characteristics of an organism are controlled by
single-locus allele sets rather than polygenes.
- Less essential characteristics are controlled by polygenes (multi-loci gene
alleles scattered over a number of different loci).
- An unknown number of color characteristics rely on polygenes, which
take the form of plus or minus modifiers to alter the expression of a
characteristic whose basic form was set by a major gene.
- The "S" Gene Locus (Spotting Series) is the most researched set of color
polygenes in dogs. These polygenes vary the expression of S locus genes,
which create varying amounts of white spotting on the dog. Ignoring the very
rare albino and blue-eyed albino genes, there are usually four main genes
listed at this locus, but Robinson has identified at least ten degrees of
identifiable spotting. It is believed that adjustments are made to the
main genes by modifying polygenes at a number of other loci, each of which
can contain a "minus modifier" (which decreases spotting), or a "plus modifier"
(which increases spotting).
- Anatolian Shepherds as a breed appear to have the full spectrum of spotting
genes as well as the gene coding for solid color. With enough plus modifiers
in an otherwise genetically solid colored dog, white areas can appear on feet,
chest, tail tip, and perhaps elsewhere. With a sufficient number of plus
modifiers, white can even look like the next level of spotting.
- Polygenes, including the ones that affect hip dysplasia, are difficult to
eliminate from the genetic pool without a reliable genetic test. When two
animals with many minus modifiers and few plus modifiers are mated, one or
more of their offspring may get all of the plus modifiers. These "plus modifier"
pups would be much more affected than either parent.
- Breeding rules are more reliable when all the genes affecting a characteristic
are found at one locus than when the genes are polygenes.
- The rufus polygenes
The rufus polygenes determine whether the coat is fawn or red or some shade in
between. In addition to the major coat lightening genes, such as the chinchilla
gene (c ch) in at the C gene locus (The Albino Series) mentioned
above, there is a set of polygenes in which the combination of plus and minus
modifiers makes the coat vary from paler yellow (light fawn) through deeper
red (red). It is reported that on an individual gene basis the fawn may be
dominant over the red. However, a dog with plus modifiers at a majority of the
loci will be red (the more plus modifiers the deeper red the dog will appear).
It is possible that only dogs without the chinchilla (cch) gene can
reach the deep, dark red color rarely seen in Anatolian Shepherds.
- The umbrous polygenes
The umbrous polygenes determine the extent of dark shading (black or brown
pigment) present on a fawn background (red/yellow pigment). The type of light
pigment present in many Anatolian Shepherds (from the influence of "AY,"
the "A" gene locus [The Agouti Series]) allows for the presence of sabling
(dark tipped hairs) and sailing (longer black hairs on a fawn background). This
dark shading varies from visually absent through very heavy shading. This
variation in shading is attributed to the umbrous set of polygenes.
Umbrous polygenes may have an effect on patterns such as brindling, black mask,
or the saddle pattern, but these patterns probably have their own sets of
polygenes. In fact, the saddle pattern seen on some dogs is speculated to be
the result of polygenes alone. Also, it is speculated that polygenes affect
the width, frequency, intensity, and evenness of brindle stripes. However, no
research has been done on this aspect of coat color.
Many additional sets of polygenes are thought to exist. However, since
polygenes are more complex than the major genes, polygenes are difficult to
research. Over time, perhaps we will learn more about the full extent of their
influence.
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