UNDERSTANDING COAT COLOR
IN THE CARDIGAN WELSH CORGI
The CWCCA has voted upon various issues regarding coat color and breeding standards for our breed. Everyone is entitled to an opinion. Only educated opinions make sound decisions. Just look at the judges you see in the ring judging our breed. Everyone of them is entitled to his or her opinion. Only the educated, informed opinions have merit. This article is intended to help produce educated opinions, not to campaign for any result.
The key to understanding coat color inheritance in Cardigans is to understand that four separate and distinct genetic code groups are responsible for all of our color variations. It is the combination of these four separate code groups, and each of their components, that determine the color of a particular dog and its color reproductive capabilities.
The four independent sets of codes are:
1. Base Pattern
The Base Pattern code group has two choices: brindle or tan.
The Distribution code group has two choices: Restricted or Unrestricted.
If Restricted, the Base Pattern is limited in distribution in the coat to the "Point" area of the dog, forming our Black and White and Blue Merles, with tan or brindle points. (The "Points" are the tan or brindle markings found usually at the cheeks, eyebrows, chest, stifles and under the tail. The rest of the dogs body color is controlled by the Pigment group and is either black or chocolate. See below).
If Unrestricted, the Tan or Brindle Base Pattern is distributed throughout the body, the dog does not exhibit points and is either red/sable or brindle.
The Merle code group has two choices, On or Off.
The Pigment code group has two choices, Black or Chocolate.
Each code group is comprised of two bits of genetic information, one contributed from the sire and one from the dam. Each code group works INDEPENDENTLY from the other. Each groups resulting action on the dog is determined by the make up of its two bits of genetic information.
Each of these different code groups can be viewed as a separate set of two coins each. The "Base Pattern" code group can be compared to Half-Dollars; the "Distribution" code group can be seen as Quarters; the "Merle" code group can be viewed as Nickels and the Pigment code group can be Dimes.
Every dog will have, as its genetic color makeup, two Half-dollars, two Quarters, two Nickels and two Dimes, one and only one of each from each parent. When two dogs are bred, each parent "tosses" one of each coin, so that each coin is either "heads" or "tails". (Some dogs have only "heads" Half-dollars, some only "Tails" Half-dollars, and some will have both a "heads" and "tails" Half-dollar, depending upon what it inherited from its own parents). Each of the two choices for each of the four code groups are represented by a "heads or a "tails" coin. Thus, every puppy has two Half-dollars (the Base Pattern code group), but each may be "heads" or "tails". The same is true of each other denomination of coins, but there will always be 8 coins - two Half-dollars, two Quarters, two Nickels and two Dimes.
Imagine now that the Half-dollars which are "tails" represent the genetic bit of information for the Tan Base Pattern code and that the "heads" Half-dollars represent the Brindle Base Pattern code. Similarly, the "tails" Quarters represent the Restricted Distribution code and the "heads" Quarters represent the Unrestricted Distribution code. The "tails" Nickels represent the Off Merle code and the "heads" Nickels are the On Merle code. Finally, the "tails" Dimes are the Chocolate Pigment code while the "heads" Dimes are the Black Pigment code.
Each parent tosses one and only one Half-dollar, Quarter, Nickel and Dime into a dogs genetic makeup. The two Half-Dollars pair together, and separately from the two Quarters, Dimes and Nickels, which each pair together. You then look at the pairs of coins, one by one, to see if the coins are "heads" or "tails". The combinations of the "heads" or "tails" of the different coins determines the coat color of each individual dog.
A dog with two "tails" half-dollars (the Base Pattern code group) will have a Tan Base Pattern but if either half-dollar is "heads" the Base Pattern will be Brindle. (Brindle is "dominant" to Tan, so the existence of only one "heads" Half-dollar (brindle) will dominate the pair causing the Base Pattern of the subject dog to be Brindle). Remember, though, while it will LOOK brindle, it may have as its second coin in the Half-dollar pair a "tails" Half-dollar, so that when it is bred, it may itself toss in the "tails" Half-dollar, contributing the Tan Base Pattern to its offspring even though it is a brindle itself. Thus, two brindle dogs, each having a "tails" Half-dollar (Tan Base Pattern) to contribute, may produce a red/sable. They also may have a "tails" Quarter (Restricted Distribution) to contribute to their offspring when bred. If both brindles have "tails" Quarters and they are each contributed to the offspring when bred, the two brindle dogs will produce Restricted Distribution puppies: Black and White with Tan (or Brindle depending upon the Base Pattern Half-dollar) Points. (See Quarters below). The same is true of all of the "tails" coins, regardless of denomination.
The two Quarters contributed by the parents represent the Distribution code group. Here, Unrestricted is "dominant" to Restricted. If both Quarters are "tails", the dog will have either the Tan or Brindle Base Pattern (determined by the half-dollar Base Pattern code group) but it will be restricted to the Point areas described above. The rest of the dogs body color (either Black or Chocolate) will be as determined by the Dimes of the Pigment code group. If either Quarter is "heads", the Distribution code group will yield an Unrestricted result, and the dog will not have points because the Tan or Brindle (determined by the Half-dollars of the Base Pattern code group) will be Unrestricted and distributed throughout the body. These are our Red/Sable and Brindle (all shades) dogs.
Next is the Merle code group represented by Nickels. On is "Dominant" over Off. Thus, only if both nickels are "tails" will the dog be non-merle. If either Nickel is "heads", the Merle code group will be set On and produce a merle animal. An Off setting for this code group does not effect the coat color of the dog as determined by the Base Pattern and Distribution code group. Our Black and Whites with Tan or Brindle Points and our Red/Sables and Brindles are all set with the Off Merle code group code. An On setting here, (a "heads" Nickel), causes the merle effect on the dogs coat color as determined by the Base Pattern (Half-dollars) and Distribution (Quarters) code groups. In Restricted Distribution code group dogs the On merle will effect the Black or Chocolate (determined by the Pigment code group) left on the body after the Base Pattern has been Restricted to the Points. Thus, our Blue and Chocolate Merles, with Tan or Brindle Points. In Unrestricted Distribution code group dogs, the On Merle code group determines Sable and Ginger Merles, and the "hidden" Red Merle.
Finally, is the Pigment code group, our Dimes. Black is "dominant" over Chocolate, so if both Dimes in our stacks are "tails" the Pigment code group will be set for Chocolate. If either Dime is "heads" the Pigment code group will be set for Black. Nearly all Cardigans are Black Pigment code, but the Chocolate genetic code has long been recognized as a regularly occurring recessive in Cardigans. There is little doubt amongst those who have observed Cardigan coat color genetics over time that the Chocolate is naturally found in the breeds gene pool. We often refer to it as a "dudley". A dog which receives two "tails" Dimes from its parents, the Chocolate genetic setting, will have a Chocolate nose and eyerims and Chocolate pigment in what would otherwise be Black pigmented areas. This is the same genetic combination that creates the difference between a Red and Black Doberman Pincher and, when the Merle code group is On, between a Blue Merle and Red Merle Australian Shepherd and when the Merle code group is Off, the Black and White or Red and White Aussie.
Thus, to properly analyze a dogs genetic color one must view ALL FOUR code groups individually because they work independently of each other. You cannot think of a dog as a brindle. Rather, to understand a brindle dogs color genetics you must think of it as a dog with FOUR DIFFERENT genetic codes. Examples of the results of each of these four different groups, working with each other, are as follows:
It is the setting of each of the four code groups, each determined by the combination of the two choices for each group, that determines the genetic makeup of our dogs, their coat color appearance and their genetic capabilities of color reproduction.
UNDERSTAND CARDIGAN COAT COLOR INHERITANCE YOU MUST RECOGNIZES
THE FOUR CODE GROUPS and the two alternatives available in each
of the four code groups. We hope this exercise has helped to
explain this extremely complicated subject.
Steve & Marieann Gladstone