Border Collie Colors
BORDER COLLIE COLOR DIVISIONS FOR CONFORMATION CLASSES (05.01.2006)
AKC Parent Clubs “own” the policy on whether or not their breed may, or is required to, be divided by color in conformation classes. In 2006, BCSA sent the following letter to AKC to update the policy on the Border Collie.
BCSA has gotten feedback from exhibitors that the color class division definitions for Border Collies were unclear and confusing. The current class divisions are “Black & White” or “AOAC.” Exhibitors weren’t always sure in which class to enter tri-colored dogs. Additionally, the word “allowed” in AOAC implied that there are some colors which are not allowed, yet in the Border Collie, any color is acceptable. So, BCSA convened a committee to review the subject and propose a course of action.
This committee requested membership input, analyzed how other breeds word color division definitions and came up with a proposed change to the class definitions. It was decided to continue to allow color divisions to hopefully raise awareness that our breed comes in many colors besides the traditional black and white “tuxedo” markings and that there are no disallowed or less-preferred colors. However, we understand that at many all-breed shows, the Border Collie entry is too small to justify class division, so will continue to leave it at the show-giving club’s discretion on whether or not to divide.
We would just like to change the color definitions for those times when show-giving clubs do choose to divide on color. When a division is offered, only the Open classes shall be divided. The color classes shall be Black (including Black & White and Tri-Color). All Other Colors or AOC (note: remove the word “allowed” in the acronym).
A GUIDE TO THE GENETICS OF COLOR
The purpose of this guide is to provide some very basic information regarding the influence of genetics on coat color. It is important to emphasize that this subject is complex and confusing at best. Research is ongoing and what may be the prevailing theory today, may well be disproved in the future.
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 our Breed Color pages above.
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 makeup of an individual created by the combination of genes. Not all of
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|
|Dam is heterozygous black with brown as recessive||B||BB||BB|
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:
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, thereby 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 the 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:
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 can be seen in the Blue and Lilac dogs. If the Dilution gene acts on the brown and black coats, you can get the following: black diluted to blue and brown diluted to lilac (see photo to right).
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 black dogs carry both brown and the dilution gene.
|BbDd – The Dam can contribute:||BD||bD||Bd||bd|
|BbDd – The Sire can contribute:||BD||BBDD||BbDD||BBDd||BbDd|
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 effect 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 its 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 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.