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The Genetics of Breed Color In The American Pit Bull Terrier
by Amy Greenwood Burford B.S.


One of my responsibilities as a member of the staff of the American Dog Breeders
Association is to be the 'color expert'. I believe that my many years of experience in the breed,
as well as the opportunity to have grown up in a true 'American Pit Bull Terrier' family. has
given me the exposure that it requires to know the descriptive terms to describe the many diverse
colors in our breed. The color description that is placed on your ADBA registration papers does
not in any way attempt to depict the genetic makeup (genotype) of the individual dog. Instead it
is a description of the dogs actual color that you see (phenotype). This color description is used
for identification only and in many cases does not predict what color combinations the individual
dog will produce in its offspring.
Over the course of the last few months, I have received a surprising number of questions
concerning color and the genetic inheritance of color. Questions such as: 1. The blue color in the
APBT in the past was very rare. How are so many kennels now producing blues in such
numbers? 2. It is possible to produce a puppy with a black nose, when both parents have red
noses? 3. Where does the chocolate coloring come from? 4. How did I produce a brindle from a
line that has never had brindle dogs? In my review of the genetics of color in the American Pit
Bull Terrier, I will review a few of the principals of genetic inheritance in general and look at the
research that has been done in the field of color genetics in our breed in an attempt to give our
readers a better understanding of color genetic as well as provide answers to the above questions.
GENETIC PRINCIPALS
Each offspring inherits one half of their genetic make-up from their sire and one half
from their dam. All members of the genus canis, to which all dog breeds belong have 78
chromosomes. They appear in pairs and consist of chains of DNA material. Small sections of
these DNA chains make up genes, the genetic code for the production of certain proteins in the
individual dog. The genetic material for particular traits in the dog are located in certain regions
on the chromosomes called loci (plural) or locus (singular). The different assortment of genes
that are possible are a particular locus are called alleles. In many different breeds, through
selective breeding, only one allele is found at a particular loci, leading to all members of the
breed having the same trait. This is why purebred dogs will breed true, for those characteristics
that distinguish one breed from another. Alleles exhibit a dominance relationship when paired
with a different allele. When the alleles are different at the same loci, they are said to be
heterozygous. When the alleles are alike at the same loci, they are said to be homozygous.
Dependent upon how many different alleles are possible there are multiple combinations of
dominance. The term epistatic (above), means more dominant and hypostatic (below) means less
dominant. Geneticists use an upper case letter: example (A), to signal a dominant allele, and a
lower case letter: example (a) to denote a recessive allele.
The study of color genetic within a breed can be complex, as there are nine different
locations (loci) on the chromosomes that effect the final color that you see in your dog. At each
loci are two or more alleles, or gene choices, that interact according to their dominance-recessive
relationships. At loci that have more than two alleles, the relative dominance in the series have
been listed in order of their dominance.
Genetic research into the genotypes of coat color has not been done with UKC or ADBA

registered APBT. The reason is this: throughout the history of our breed, dogs have not been
bred for color. All colors were considered equal. An individual dog was selected as breeding
stock based upon a multitude of factors, none of them being color. The canine genetic research
into the genotype of color has been done solely in AKC registered breeds. One of the breeds that
has been studied is the American Staffordshire Terrier. As a matter of review, it is important to
understand that every dog accepted into the AKC registry as an American Staffordshire Terrier
was also registered with the UKC or ADBA as an American Pit Bull Terrier. The year was 1936,
and the popularity of the Our Gang Comedy and show's mascot, Petey, prompted the AKC to
open their stud book to the breed as long as the breed name could be changed to the American
Staffordshire Terrier. No other breed has been crossed into the AKC American Staffordshire
Terrier lines, so we are justified in examining the results of this research and applying it to our
ADBA registered dogs. The researched results of the color genotypes possible in our breed, at
the nine loci responsible for the determination of color are presented below:
As/Ay/at, B/b, C, D/d, E/Ebr/e, g, m, S/si/sp/sw, t
 

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Locus A Series: Dark Pigment Pattern
This locus has six different alleles possible in the canine population. Only three are present in the
APBT breed.
(As) dominant Black
(Ay) dominant Yellow
(at) bicolored pattern (tan ‘Doberman like’ markings on a solid coat)
The A alleles are pattern factors that control the amount and area distribution of dark and light
pigment. They act within the hair follicle to switch pigment synthesis between light and dark. It
is important to remember that alleles at this locus interact with Locus E alleles.
(As) - DOMINANT BLACK: This allele produces uniform coverage of dark pigment over the
entire body. Its action is expressed in all dogs with black or brown coats. The (As) allele is
almost completely dominant over others in the A series. The black color ranges from pure black
to a black with a brownish cast (seal). Geneticists are uncertain if the allele is incapable to
produce pure black without additional help from another locus, or if the brown cast indicates a
heterozygous allele.
(Ay) - DOMINANT YELLOW: The (Ay) allele restricts dark pigment, producing yellow
colors. When homozygous, the coat can be clear gold, but often has black tipped hairs, especially
on the head and down the back.
(at) - BLACK AND TAN PATTERN (BICOLORED): The typical tan points are above each
eye, on each cheek, on the lips and lower jaw, extending under the throat, two spots on the chest,
below the tail, and on the feet to the pasterns and hocks, extending up the inner sides of the legs.
These tan points can occur on black or seal, blue, chocolate or red solid colored dogs. A great
deal of variation can occur with these tan points, even within the depth of the pigment. In some
dogs the tan points are not always marked and the color contrast is not always distinct.
Locus B Series - Black/Brown Pigment
(B) black pigment
(b) brown pigment
This locus contains only two alleles, the dominant (B) producing black skin and nose pigment
and the (b) recessive allele, producing brown pigment. In dogs that are red or buckskin, the
Locus (B) alleles are expressed in skin color, most visible around the eyes and nose. The black

nose indicates the genotype is (BB) or (Bb), both which would be expressed as black nose
because of the dominance of the (B) allele. A light brown or red nose is (bb), or homozygous
recessive. Being homozygous recessive, both parents must contribute one recessive (b) gene to
the offspring to produce the red nose. When breeding two dogs with the (bb) genotype, the only
resulting combination in the pups would be ( bb) or red nose.
Locus C: Pigment depth
The Locus C series controls the production of pigment throughout the coat. In dogs, the
expression of the Locus C alleles is based on observation rather than experimental studies. The
American Staffordshire Terrier breed is felt to have only the dominant (C) allele at this locus.
The C allele allows the full expression of color, of dark and light pigments. The allele (cch) or
Chinchilla Dilution, found in other breeds at this locus, causes the light pigments to be diluted
out in various degrees. This would account for the varying shades found in many littermates
depending on their homozygous or heterozygous pairing. The chinchilla dilution allele (cch)
does not affect the dark pigment, thus allowing for the white dog with black skin pigment and
black nose. Other researchers (Robinson) feel that other modifier polygenes are responsible for
this phenotype.
CC full color
Ccch medium shade
cchcch pale shade
Locus D pair: Pigment density
(D) intense pigment density
(d) dilute pigment density
The locus D pair modifies the density of the pigment. The dominant (D) gives full density in
both the heterozygous (Dd) or the homozygous (DD) combination. The homozygous recessive
(dd) alleles dilute the color. When the dogs basic color is produced by dark pigment, genotype
(Bbdd) or (BBdd) yields the color known as blue. The black coat is modified as well as the skin
pigment to a gray or blue pigment around the eyes, pads and nose. When the dogs basic color is
produced by a light pigment the genotype bbdd (dilute brown pigment) produces a fawn with a
silvery cast known in our breed as a fawn/bluies. The skin pigment around the eyes is flesh
colored as well as a red or brown colored nose.
Locus E Series: Extension
(Em) black mask
(Ebr) brindle
(E) extension of dark pigment
(f) restriction of dark pigment
The Locus E alleles affect the extension of dark pigment, and all of the alleles at this locus
interact with those of locus A.
(Em) - BLACK MASK: This allele is dominant to all others in the series and is expressed as a
black mask on dogs that are not solid black. One researcher, Robinson, considers the evidence
that the black mask belongs in the E series as unconvincing and assigns it to a different series.
(Ebr) - BRINDLE PATTERN: The brindle allele produces the brindle pattern with stripes or
bars of dark pigment on a background of light pigment. In dogs with the dominant (As) allele,
which produces a solid coat of dark pigment (brown or black), the (Ebr) allele is masked because
 

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there is no light pigment on which it can act. It is dominant over the extension (E) allele. In our
breed, interactions with alleles at the B and D loci produce a rich variety of brindle colors:
Ay-B-D-Ebr- black brindle
Ay-B-ddEbr- blue brindle
Ay-bbD-Ebr- brown or chocolate brindle
Ay-bbddEbr- fawn brindle
(The (-) as the second allele at the locus pair denotes an allele that is uncertain because of the
dominant nature of the first allele. It could be homozygous or heterozygous with any of the other
alleles.)
(E) - EXTENSION: The E allele produces normal extension or expression of dark pigment. It
interacts with Locus A alleles to produce a variety of effects:
As-E- black/brown
Ay-E- red or buckskin with or without black ticked hairs (on head and back) referred to
as sable in other breeds
(ee) - RESTRICTION: The homozygous (ee) alleles restricts the expression of dark pigment,
producing the yellow shades by light pigment. It does allow the expression of dark pigment on
the nose, lips and eye rims. It is recessive to all other alleles in the E series. Homozygous (ee)
alleles interferes with the expression of most Locus A alleles.
As-ee buckskin
Ay-ee light tan
Locus G pair: Progressive Graying
(g) uniform color throughout life
Research concludes that the AST breed are homozygous (gg) with dogs retaining their coloring
throughout their lifetime. The G dominant allele present in other breeds produces a silvering or
graying of the coat over time and the recessive (g) allele, giving a uniform color throughout the
dogs lifetime.
Locus M Pair: Merle Pattern
(m) uniform pigment
Research has shown that our breed has only the recessive (m) allele at this locus. The
homozygous recessive (mm) produces a uniform pigment in the breed. The (M) dominant allele
produces the merle or dapple pattern. The dominant (M) allele has been identified in Collies,
Shetland sheepdogs, Australian Shepherds, Cardigan Welsh Corgis, Great Danes, Louisiana
Catalhoula, Spotted Leopard Dogs and Dachshunds.
Locus T Pair: Ticking
(t) no ticking
Research has shown that our breed has only the recessive allele (t) at this locus which in the
homozygous recessive (tt) allows no ticking. The dark ticking that we see in our breed is
determined on the Locus A series by the dominant (As) allele, not on the Locus T Pair. In some
breeds this is known as a sable. In the APBT, traditionally this coloring is called black or brown
ticked. There are modifier polygenes that control the location and extent of the black ticking in
the breed. The dominant (T) allele at this locus causes the tiny flecks of pigmented hair in
otherwise non pigmented (or white) areas. The T allele is typical in breeds such as the English
setter and many of the hound breeds.

Locus S Series: White Pattern
The alleles of the Locus S series produce the white markings that are often seen in our breed.
Researchers identify four alleles at this locus:
S solid color
si Irish spotting
sp piebald spotting
sw extreme piebald spotting
The above sequence reflects the decreasing areas of pigmented hairs. There is some question
about the relative dominance of and interaction between the alleles in their heterozygous forms
because the expression is complicated by modifier polygenes which affect all of the alleles. Our
breed, which research shows carries all four of the alleles, show all ranges of white markings
from solid colors to all white.
(S)- SOLID COLOR: The homozygous (S) alleles produce a solid colored coat. The modifiers
will, on occasion, produce a small amount of white markings on the throat, chest, toes, abdomen
and belly.
(si) - IRISH SPOTTING PATTERN: This allele produces a pattern of white on the muzzle,
forehead, chest, belly, feet and tail tip. The varying size of the white area is affected by the plus
and minus modifiers. Breeds thought to be homozygous for this are the Boston Terrier, Basenjis
and Collies.
(sp) - PIEBALD SPOTTING PATTERN: This allele produces a widely varying areas of
white. In the homozygous (spsp) genotype you would see a white dog with dark patches.
(sw) - EXTREME PIEBALD SPOTTING PATTERN: This allele further decreases the
pigmented area and, depending on the plus or minus modifiers, the pattern can range from solid
white to white with spots on the ears, around the eyes, and in the tail area.
GENOTYPE SUMMARY in the American Staffordshire Terrier:
Black As-D-EBlue
As-ddEBlack
& Tan atatD-ERed
AyD-EFawn
AyddEBrindleAy-
D-Ebr-
Blue Brindle Ay-B-ddEbr-
CONCLUSION:
Question # 1: In times past, the blue color was considered as rare in the breed. How are
kennels now producing blue dogs in such great numbers?
The D Locus pair is the loci that modifies the dark Pigment pattern to blue with the
homozygous recessive (dd) alleles. Because kennels are selecting blue individuals which are
homozygous recessive (dd) the only allele that a blue parent can give to their offspring is the
recessive (b) allele. Breeding two blues together doubles up the recessive trait to (dd) whichmodifies the dominant (As) allele to blue. If a resulting offspring happens to get the (Ay) allele
from one of its parents, then the (dd) will modify this color to a fawn/bluies. If breeders are
breeding dogs for the blue color, since the gene is homozygous recessive, 100% of their
offspring will be (dd) and depending on the (As) or (Ay) allele on the Locus A series will have
blue or fawn/bluies pups.
Question # 2: It is possible to produce a puppy with a black nose from two parents, both
with red noses?
The red nose in our breed is produced from the Locus B pair with the homozygous recessive
(bb) genotype in combination with the (Ay-) genotype. Mating two dogs with the genotype (bb)
the result would be 100% of the pups having red noses (bb). If a pup with a black nose was
produced in one of my litters where both parents had red noses, then DNA testing with
parentage verification would be necessary to determine the actual sire to the black nose pup.
New alleles can be produced through mutation, but proof of parentage would have to be
determined using DNA to rule out a duel sired litter.
Question # 3: Where does the chocolate color come from?
The chocolate color comes from the Locus B pair with the homozyous recessive (bb) in
combination with the (As) allele. The dilution gene (dd) will also modify this dark chocolate to
a light or almost milk chocolate. In most cases, the nose color is also light brown or as we say
‘chocolate/red nose’.
Question # 4: How did I produce a brindle from a line that has never had brindle dogs?
The Locus E Series (Ebr) allele causes the brindle color pattern when this dominant allele is
present in combination with the (Ay) allele. The (Ebr) allele is dominant except in dogs with
the (As) allele. In the case of the (As), the (Ebr) allele does not have a light pigment to work
on, the brindle will remain hidden. In tracing a brindle dogs bloodline, somewhere in the
generations you should see a brindle dog since the (Ebr) allele is dominant. Again, if this was
my litter, I would ask for parentage verification using DNA to rule out a dual sired litter.
In conclusion, I would like to advise breeders to look beyond a dog color in determining quality
in terms of breeding stock. Selection should be made looking to breed type, temperament,
structural soundness and overall health in that order. If the colors of the pups that result from
your breeding ‘Just doesn’t make sense’, invest in parentage verification using DNA testing.
The cost is cheap, and the peace of mind is great.
Want to learn more? Contact the ADBA for a list of references.
 

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If this has already been posted I apologize for posting it up twice as I don't go looking back through the forum to see if it's been put up or not. We have a lot of people ask questions about colors and how blue became so popular in the breed when it was once so rare. Well this sums it up to the extent we can trace it back in the breed which is believed to have gotten into the gene pool through the Blue Paul.
 

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Good read! This is the article I got my response for that blue/red nose thread in General a few days ago and the blue dog thread in VIP. Excellent info!
 

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Yeah I am now seeing alphabet stars around my head after reading it LOL.
OMG I know they all start running together and pretty soon "Ay-B-D-Ebr" are no longer letters. They translate to me as blaaaaaaahdkjak vk jc ckaolblaaaaaaaaaaaah lol Saying a word too many times in my head when I am writing papers and stuff turn into the same thing. They just lose all meaning whatsoever..... Bllllllaaaahhhh....
Ok I'm done. I think I am the only person this happens to because everyone looks at me crazy when I say that.
 

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ahhh ha... so bunny is a SW (extreame pie bald spotting pattern)
 

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Great reading!!
 
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