A BASIC GUIDE TO COAT COLOR GENETICS
The purpose of this guide is to provide some VERY basic information regarding how genetics influences coat color in
Border Collies. It will also attempt to simplify some of the scientific terminology used to “explain” how these various
colors are produced. It is important to emphasize that the genetic basis of coat color is very complex and confusing at
best. Research is on going and what may be the prevailing theory today may well be disproved in the future.
There are individuals who have put a great deal of time and energy into the study of “color” genetics and the
information found on their websites is very informative and much more detailed than you will find in this guide.
Understanding concepts of inheritance must first start with learning to speak the “language” of genetics.
IT STARTS WITH DNA
In sexual reproduction, genetic material from the sire and dam are passed on to their offspring in the form of DNA.
The makeup of DNA consists of two strands of genetic material that connect to each other forming what is known as
“base pairs”. How these base pairs align with each other, become the genetic blueprint for a particular trait. These
aligned base pairs of DNA (one from each parent) are called GENES. Genes are located within chromosomes. A
GENE LOCUS is where a gene is located on a chromosome. One published analogy likened a chromosome to a
music CD; the genes found on the chromosome, occupy a specific location or “locus” much like music is found on a
specific track. This is an important concept to keep in mind, when we talk about the different GENE SERIES OR LOCI
later in this guide.
PHENOTYPE:
Phenotypes are the physical characteristics, created by the combination of genes that can be “observed” about an
individual (such as hair or eye color).
GENOTYPE:
The genetic make up of an individual created by the combination of genes. Not all of the characteristics are visible,
such as being a “carrier” of a certain disease or color.
ALLELE
Different versions of a gene for the same trait, such as color, which gives rise to different phenotypes, are known as
alleles. The individual will have two alleles for each trait as one is inherited from each parent. Alleles may be
dominant or recessive.
DOMINANT AND RECESSIVE:
An allele is dominant if it “show’s itself” and hides the presence of another allele. For example, if a dog has a copy of
a black gene and copy of a brown ** gene, the dog will be black because black is dominant to brown (recessive). You
cannot tell by looking at the dog if they have a copy of the brown gene (genotype). An allele is recessive if its effect is
not seen when a more dominant allele is present, as in the brown example above. For the dog to be brown, he must
have two copies of the brown gene. NOTE: in the United States, the traditional nomenclature for a Border Collie that
is brown in color is to call them RED and they are registered as such. However, due to the fact that they are
considered “brown” genetically (genetic code “bb”), that is the term that will be used in this guide.
HETEROZYGOUS:
When the two genes making up an allele are different, such as “Bb” (Black as dominant and brown as recessive), it is
referred to as being heterozygous for that gene.
HOMOZYGOUS:
When the two genes making up the allele are identical, such as “bb” (both genes recessive for brown), it is referred to
as being homozygous for that gene.
Therefore, when a dog is heterozygous for a specific gene, statistically it will pass the dominant copy to half its
offspring and the recessive copy to the other half. When it is homozygous for a particular gene, it will pass this copy
to its entire offspring.
PUNNETT SQUARE:
This is a commonly used diagram to demonstrate genetic combinations that are possible using the concepts of
dominant and recessive (expressed in percentage of probability) Here is an example:
SIRE is Homozygous black
B B
DAM is B
Heterozygous
Black with
Brown as b
Recessive
When you look at the genetic possibilities, you will see that all the puppies will be Black (phenotype) and two will carry
brown color as recessive traits (genotype).
If both parents were heterozygous Black, carrying brown recessively, the combinations would look like this:
SIRE
B b
DAM B
b
This demonstrates that statistically, three dogs would be Black, one would be brown and three would be carriers of
brown.
COLORS AND PATTERNS
The substance that gives a dog’s hair its color is called MELANIN. There are two types of melanin in the dog:
EUMELANIN: The dark pigments of Black and Brown
PHAEOMELANIN: A yellow or red color
Note: Both of these pigments can be acted upon by other genes, there-by altering these “base” colors (discussed
later).
Only the dominant version of the color gene results in eumelanin production. If the dog has two copies of the
recessive version, he will have no eumelanin, and his hair will contain only the light pigment. His nose leather and eye
rims will be red or brown
There are also Pattern genes that affect the distribution of a particular color on the dog. Both the color and pattern of
a dog is determined by several Loci or gene series. There is no “single” gene that dictates coat color, but rather a
combination of genes that are either expressed or carried that determines the color and pattern of the offspring.
The following is a very basic discussion that addresses some, but not all, of the Loci and the influence they exert in
the total “equation” that makes up colors and patterns. Included in some cases, will be the genetic “coding” used to
represent part or all of a dog’s color genotype but it is NOT an all-inclusive list of the genetic possibilities.
A (Agouti).
This locus is responsible for how pigment is distributed along the dog’s hair shaft and body regions, by inhibiting
eumelanin (dark pigment) production. This locus is involved with Sable dogs (both shaded and clear), Saddleback
Sable, and “Tan points”.
You will see the following “coding” used to indicate these colors/patterns:
A^y Sable
Ay^Ay clear sable
Ay^at shaded sable (sable with dark fur in coat).
“a^t” tan points
“a^s” saddleback pattern
Dominant Black (K)
This gene turns the “Agouti” genes on and off and codes are:
Black (Agouti genes “off”; not expressed) and
Brindle (Agouti genes “on; expressed) code: br^k
As well as combinations of the above as “expressed” or “carried”
Example: K^br is a black dog carrying brindle.
Kk^Ayat is a black dog carrying sable and tricolor
Brindle is a pattern of alternating stripes of eumelanin and phaeomelanin pigmentation (yellow/black, or red/black)
B Locus (Brown)
This gene determines or selects for a black or brown dog. When this gene is in its dominant form (BB or Bb) the dog
is black. When this gene is in its homozygous recessive form (bb) it has a lightening effect on the eumelanin only and
the dog is brown.
BB is homozygous Black (not carrying brown)
Bb is heterozygous Black (carrying brown)
bb is homozygous Brown.
D Locus:
This dilution gene acts on both eumelanin and phaeomelanin pigments. It “dilutes” the base color of the dog. If the
dog is “D” or dominant, it is fully pigmented. If the dog is “dd”, this recessive gene dilutes the pigment, thereby
altering its color. In Border Collies, the d/d gene is associated with skin problems such as Color Dilution Alopecia or
hair loss (on the ears is common) which is often seen in the Blue and Lilac dogs.
If the Dilution gene acts on the brown and black coats, you can get the following:
A black dog diluted to a BLUE
A brown dog diluted to LILAC.
Lilac is caused primarily by a “double recessive” condition of bb at the B gene locus and dd at the Dilute gene locus.
It is also possible to produce a Lilac color out of pairings of black-to-black, black to brown, brown-to-brown, black to
blue and blue to brown IF the genes are paired correctly AND they both carry the recessive forms of the B and the D
gene (“b” and “d”)
To demonstrate the genetic possibilities as mentioned above, let's make both the sire and the dam genotypes the
same as BbDd. These are black dogs that carry both brown and the dilution gene.
BbDd
The Dam can contribute:
BD bD Bd bd
BbDd
Sire BD BBDD BbDD BBDd BbDd
Can Black Black Black Black
Contribute
bD BbDD bbDD BbDd bbDd
Black Brown Black Brown
Bd BBDd BbDd BBdd Bbdd
Black Black Blue Blue
bd BbDd bbDd Bbdd bbdd
Black Brown Blue Lilac
In this case, Black is dominant (B). If it is acted on by the dilution gene (dd), it will produce a Blue dog. Brown is
recessive (bb) and if it is acted on by the dilution gene (dd), it will produce a lilac dog. If the black or the brown dog
has Dd, where D indicates the dog is fully pigmented, they retain their base color.
If we were to express the above diagram in statistical probability:
56% of the offspring would be black, 19% would be brown, 19% would be blue and 6% would be lilac.
Keep in mind that the example above is only showing the B and D gene series affect on the genotype. Other gene
series influence and are a part of the total “picture”
If the Dilution gene acts on the light coat (phaeomelanin) it will dilute a red color to cream (for the description of the
red color, see the E locus).
E Locus:
This gene series either restricts or extends pigments in the hair follicle. If it is in its dominant form (E), it extends the
darker pigment (Black or Brown dog). If it is in it’s recessive form (e/e), it allows only the extension of the
phaeomelanin, and the dog’s color becomes what is called a TRUE RED, Australian Red or in the United States,
“Gold”.
This gene is considered a “masking” gene as it will hide a dog’s true color. However, it only affects the hair follicle so
you can identify its color by the nose leather and eye rims. For example, a dog that is genetically Brown, will have
brown or reddish nose leather /eye rims but has a golden to red coat color. If it also has the dilution gene, the coat
will be a creamy color. Its genetic code might look like “b/b, d/d, e/e”.
S Locus:
The S gene series demonstrates various patterns of white spotting. This includes the traditional white markings seen
on black border collies, often called Tuxedo Markings or Irish spotting as well as the piebald spotting pattern and the
extreme white spotting pattern.
The coding is as follows:
s^i tuxedo markings
s^p piebald spotting where there are random spots of color on a
white background.
s^w a dog that is almost completely white.
Currently, Border Collies that have extreme amounts of white and or white that crosses the flank in lines or patches
are referred to as being “white factored.” Having increased white areas is not a problem per se, however from a
breeding perspective, there is research-linking deafness to the alleles for piebald spotting or extreme whiteness.
T Locus
The T series refers to “ticking” or flecks of color in white areas.
Code for Ticked is T^T (and non-ticked is t/t)
M locus:
The Merle gene is a pattern gene, not a color in of itself. It is also a dilution gene. It causes patchy areas of color
dilution, resembling a marble like pattern. This will result in a genetically black dog to show grey patched with black
areas and they will have a black nose. If the dog is genetically blue, he will have grey patched with dark blue/grey
areas and a grey nose (commonly called a Slate Blue). Both are referred to as BLUE MERLES. A genetically brown
dog will show patchy cinnamon/brown/red patches and they will have a liver colored nose (RED MERLE). A
genetically SABLE dog would be called a SABLE MERLE, however, with the phaeomelanin dominating the color
scheme, they are often difficult to recognize as adults.
Only a merle parent can produce a merle puppy…It is not a gene that is “carried”, therefore, the coding would be M
for Merle or “m” for non-merle.
Breeding a merle to a merle is not recommended as the offspring can have a significant risk of health problems.
Summary of the Loci or Gene Series:
A and E Loci control pigment distribution
B, D, M Loci modify color by “dilution”
S and T Loci control placement of white areas.
Border Collies. It will also attempt to simplify some of the scientific terminology used to “explain” how these various
colors are produced. It is important to emphasize that the genetic basis of coat color is very complex and confusing at
best. Research is on going and what may be the prevailing theory today may well be disproved in the future.
There are individuals who have put a great deal of time and energy into the study of “color” genetics and the
information found on their websites is very informative and much more detailed than you will find in this guide.
Understanding concepts of inheritance must first start with learning to speak the “language” of genetics.
IT STARTS WITH DNA
In sexual reproduction, genetic material from the sire and dam are passed on to their offspring in the form of DNA.
The makeup of DNA consists of two strands of genetic material that connect to each other forming what is known as
“base pairs”. How these base pairs align with each other, become the genetic blueprint for a particular trait. These
aligned base pairs of DNA (one from each parent) are called GENES. Genes are located within chromosomes. A
GENE LOCUS is where a gene is located on a chromosome. One published analogy likened a chromosome to a
music CD; the genes found on the chromosome, occupy a specific location or “locus” much like music is found on a
specific track. This is an important concept to keep in mind, when we talk about the different GENE SERIES OR LOCI
later in this guide.
PHENOTYPE:
Phenotypes are the physical characteristics, created by the combination of genes that can be “observed” about an
individual (such as hair or eye color).
GENOTYPE:
The genetic make up of an individual created by the combination of genes. Not all of the characteristics are visible,
such as being a “carrier” of a certain disease or color.
ALLELE
Different versions of a gene for the same trait, such as color, which gives rise to different phenotypes, are known as
alleles. The individual will have two alleles for each trait as one is inherited from each parent. Alleles may be
dominant or recessive.
DOMINANT AND RECESSIVE:
An allele is dominant if it “show’s itself” and hides the presence of another allele. For example, if a dog has a copy of
a black gene and copy of a brown ** gene, the dog will be black because black is dominant to brown (recessive). You
cannot tell by looking at the dog if they have a copy of the brown gene (genotype). An allele is recessive if its effect is
not seen when a more dominant allele is present, as in the brown example above. For the dog to be brown, he must
have two copies of the brown gene. NOTE: in the United States, the traditional nomenclature for a Border Collie that
is brown in color is to call them RED and they are registered as such. However, due to the fact that they are
considered “brown” genetically (genetic code “bb”), that is the term that will be used in this guide.
HETEROZYGOUS:
When the two genes making up an allele are different, such as “Bb” (Black as dominant and brown as recessive), it is
referred to as being heterozygous for that gene.
HOMOZYGOUS:
When the two genes making up the allele are identical, such as “bb” (both genes recessive for brown), it is referred to
as being homozygous for that gene.
Therefore, when a dog is heterozygous for a specific gene, statistically it will pass the dominant copy to half its
offspring and the recessive copy to the other half. When it is homozygous for a particular gene, it will pass this copy
to its entire offspring.
PUNNETT SQUARE:
This is a commonly used diagram to demonstrate genetic combinations that are possible using the concepts of
dominant and recessive (expressed in percentage of probability) Here is an example:
SIRE is Homozygous black
B B
DAM is B
Heterozygous
Black with
Brown as b
Recessive
When you look at the genetic possibilities, you will see that all the puppies will be Black (phenotype) and two will carry
brown color as recessive traits (genotype).
If both parents were heterozygous Black, carrying brown recessively, the combinations would look like this:
SIRE
B b
DAM B
b
This demonstrates that statistically, three dogs would be Black, one would be brown and three would be carriers of
brown.
COLORS AND PATTERNS
The substance that gives a dog’s hair its color is called MELANIN. There are two types of melanin in the dog:
EUMELANIN: The dark pigments of Black and Brown
PHAEOMELANIN: A yellow or red color
Note: Both of these pigments can be acted upon by other genes, there-by altering these “base” colors (discussed
later).
Only the dominant version of the color gene results in eumelanin production. If the dog has two copies of the
recessive version, he will have no eumelanin, and his hair will contain only the light pigment. His nose leather and eye
rims will be red or brown
There are also Pattern genes that affect the distribution of a particular color on the dog. Both the color and pattern of
a dog is determined by several Loci or gene series. There is no “single” gene that dictates coat color, but rather a
combination of genes that are either expressed or carried that determines the color and pattern of the offspring.
The following is a very basic discussion that addresses some, but not all, of the Loci and the influence they exert in
the total “equation” that makes up colors and patterns. Included in some cases, will be the genetic “coding” used to
represent part or all of a dog’s color genotype but it is NOT an all-inclusive list of the genetic possibilities.
A (Agouti).
This locus is responsible for how pigment is distributed along the dog’s hair shaft and body regions, by inhibiting
eumelanin (dark pigment) production. This locus is involved with Sable dogs (both shaded and clear), Saddleback
Sable, and “Tan points”.
You will see the following “coding” used to indicate these colors/patterns:
A^y Sable
Ay^Ay clear sable
Ay^at shaded sable (sable with dark fur in coat).
“a^t” tan points
“a^s” saddleback pattern
Dominant Black (K)
This gene turns the “Agouti” genes on and off and codes are:
Black (Agouti genes “off”; not expressed) and
Brindle (Agouti genes “on; expressed) code: br^k
As well as combinations of the above as “expressed” or “carried”
Example: K^br is a black dog carrying brindle.
Kk^Ayat is a black dog carrying sable and tricolor
Brindle is a pattern of alternating stripes of eumelanin and phaeomelanin pigmentation (yellow/black, or red/black)
B Locus (Brown)
This gene determines or selects for a black or brown dog. When this gene is in its dominant form (BB or Bb) the dog
is black. When this gene is in its homozygous recessive form (bb) it has a lightening effect on the eumelanin only and
the dog is brown.
BB is homozygous Black (not carrying brown)
Bb is heterozygous Black (carrying brown)
bb is homozygous Brown.
D Locus:
This dilution gene acts on both eumelanin and phaeomelanin pigments. It “dilutes” the base color of the dog. If the
dog is “D” or dominant, it is fully pigmented. If the dog is “dd”, this recessive gene dilutes the pigment, thereby
altering its color. In Border Collies, the d/d gene is associated with skin problems such as Color Dilution Alopecia or
hair loss (on the ears is common) which is often seen in the Blue and Lilac dogs.
If the Dilution gene acts on the brown and black coats, you can get the following:
A black dog diluted to a BLUE
A brown dog diluted to LILAC.
Lilac is caused primarily by a “double recessive” condition of bb at the B gene locus and dd at the Dilute gene locus.
It is also possible to produce a Lilac color out of pairings of black-to-black, black to brown, brown-to-brown, black to
blue and blue to brown IF the genes are paired correctly AND they both carry the recessive forms of the B and the D
gene (“b” and “d”)
To demonstrate the genetic possibilities as mentioned above, let's make both the sire and the dam genotypes the
same as BbDd. These are black dogs that carry both brown and the dilution gene.
BbDd
The Dam can contribute:
BD bD Bd bd
BbDd
Sire BD BBDD BbDD BBDd BbDd
Can Black Black Black Black
Contribute
bD BbDD bbDD BbDd bbDd
Black Brown Black Brown
Bd BBDd BbDd BBdd Bbdd
Black Black Blue Blue
bd BbDd bbDd Bbdd bbdd
Black Brown Blue Lilac
In this case, Black is dominant (B). If it is acted on by the dilution gene (dd), it will produce a Blue dog. Brown is
recessive (bb) and if it is acted on by the dilution gene (dd), it will produce a lilac dog. If the black or the brown dog
has Dd, where D indicates the dog is fully pigmented, they retain their base color.
If we were to express the above diagram in statistical probability:
56% of the offspring would be black, 19% would be brown, 19% would be blue and 6% would be lilac.
Keep in mind that the example above is only showing the B and D gene series affect on the genotype. Other gene
series influence and are a part of the total “picture”
If the Dilution gene acts on the light coat (phaeomelanin) it will dilute a red color to cream (for the description of the
red color, see the E locus).
E Locus:
This gene series either restricts or extends pigments in the hair follicle. If it is in its dominant form (E), it extends the
darker pigment (Black or Brown dog). If it is in it’s recessive form (e/e), it allows only the extension of the
phaeomelanin, and the dog’s color becomes what is called a TRUE RED, Australian Red or in the United States,
“Gold”.
This gene is considered a “masking” gene as it will hide a dog’s true color. However, it only affects the hair follicle so
you can identify its color by the nose leather and eye rims. For example, a dog that is genetically Brown, will have
brown or reddish nose leather /eye rims but has a golden to red coat color. If it also has the dilution gene, the coat
will be a creamy color. Its genetic code might look like “b/b, d/d, e/e”.
S Locus:
The S gene series demonstrates various patterns of white spotting. This includes the traditional white markings seen
on black border collies, often called Tuxedo Markings or Irish spotting as well as the piebald spotting pattern and the
extreme white spotting pattern.
The coding is as follows:
s^i tuxedo markings
s^p piebald spotting where there are random spots of color on a
white background.
s^w a dog that is almost completely white.
Currently, Border Collies that have extreme amounts of white and or white that crosses the flank in lines or patches
are referred to as being “white factored.” Having increased white areas is not a problem per se, however from a
breeding perspective, there is research-linking deafness to the alleles for piebald spotting or extreme whiteness.
T Locus
The T series refers to “ticking” or flecks of color in white areas.
Code for Ticked is T^T (and non-ticked is t/t)
M locus:
The Merle gene is a pattern gene, not a color in of itself. It is also a dilution gene. It causes patchy areas of color
dilution, resembling a marble like pattern. This will result in a genetically black dog to show grey patched with black
areas and they will have a black nose. If the dog is genetically blue, he will have grey patched with dark blue/grey
areas and a grey nose (commonly called a Slate Blue). Both are referred to as BLUE MERLES. A genetically brown
dog will show patchy cinnamon/brown/red patches and they will have a liver colored nose (RED MERLE). A
genetically SABLE dog would be called a SABLE MERLE, however, with the phaeomelanin dominating the color
scheme, they are often difficult to recognize as adults.
Only a merle parent can produce a merle puppy…It is not a gene that is “carried”, therefore, the coding would be M
for Merle or “m” for non-merle.
Breeding a merle to a merle is not recommended as the offspring can have a significant risk of health problems.
Summary of the Loci or Gene Series:
A and E Loci control pigment distribution
B, D, M Loci modify color by “dilution”
S and T Loci control placement of white areas.
A RAINBOW OF COLORS
Photo courtesy of Amy Hansen of RiverRun
Border Collies
The genetics of color is a fascinating
subject, which has been oversimplified
here, in the hopes that the material is
understandable and useful. If you would
like to see examples of the colors
mentioned, please visit:
The Border Collie Society of America's
web site's color pages.
(This guide was created for the BCSA
and can be seen on their site )
Photo courtesy of Amy Hansen of RiverRun
Border Collies
The genetics of color is a fascinating
subject, which has been oversimplified
here, in the hopes that the material is
understandable and useful. If you would
like to see examples of the colors
mentioned, please visit:
The Border Collie Society of America's
web site's color pages.
(This guide was created for the BCSA
and can be seen on their site )
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