Continued from part 1
3) Stop thinking of the visible colors as one thing.
We do this a lot – somebody will say that brindle is dominant to red or similar – and sometimes it’s loosely true. But if you try to make each color its own unit, you’re going to get hopelessly confused because the real statement is always something like “Brindle is dominant to red but sometimes red looks black” and sometimes it’s “Brindle is dominant to red but sometimes brindle looks white and red looks blue.” That’s how dog breeders can be shocked by litters where a white dog is bred to a blue dog and every single puppy is dark brindle. It was never really shocking at all if you understand how the color genes work, but that breeder is probably never going to do that kind of breeding again because things “went wrong.” That’s how we end up with fear-based breeding decisions, and that’s never the right way to breed dogs.
Here’s why colors are not just one thing:
The major divisions, and remember we can think of them like the face and number cards, are called “loci” (with one of them being a locus): Essentially, a locus is where on the chromosome the color instructions sit.
In junior high biology you probably drew punnet squares, where you figured out that brown eyes are dominant to blue and so on (and if a brown-eyed kid said “But my parents both have blue eyes!” your teacher looked startled and quickly said “Oh, well, there are lots of ways that could happen; remember that we’re just learning some simple rules here!” and then booked it to the teacher’s lounge to share a certain delicious fact with others). Punnet squares are still perfectly valid when it comes to simple genes, but gene loci that have to do with color can have more than two possibilities (though only two can appear at any one time).
The loci are named with letters that refer to their function, like “A” is Agouti. I’ll put them in alphabetical order for the sake of organization but please don’t think that therefore one is more important or one was discovered first or anything.
Here are the various divisions of color, as we understand them in 2011:
I) The “A” locus. A is for Agouti, and refers to the interaction of red pigment (called phaemelanin) and black pigment (called eumelanin). Every dog on earth has genes for both types of melanin, but dogs don’t necessarily show them in equal amounts (one or both pigments may be almost or completely turned off, turned off in certain locations, fight with each other, and so on).
- Wild-type hair, designated as a^w (a with a little superscript w, which wordpress is not going to show properly so I need to use the carat. But imagine it superscripted). Wild-type hair is BANDED – the base is black, the middle is red, the top is black. Lots of hair colors have a light base and a dark tip, but only agouti has the three distinct areas. Agouti is seen in some of the primitive breeds and in dogs who are “wolf-sable.” Since the word sable also describes some of the other colors on the A locus, you need to know the difference – all banded/agouti dogs are sables but not all sables are banded/agouti. When in doubt, look for those three areas of color.
- Fawn/red/sable, designated as a^y. This is the color that most color genetics nuts like me call “sable.” These are dogs with red coloring that shades to black at the tip of the hairs; the amount of black varies from almost none to a huge amount. All of them have some black on the hairs at birth, at least along the topline. Fawn pugs, red and sable Cardigans, sable collies, Belgian Malinois, fawn and apricot Mastiffs, orange Pomeranians, and red Akitas are all sables, and all identical genetically. Don’t skip that last phrase. They are all the SAME COLOR. In Cardigans it’s common to refer to sables and reds as though they are different colors, and I’ve seen many references to the “sable gene” as being different than the red one. This is just not true. We’re not sure what makes some sables very sooty and some very clear/red, but it’s likely to be a protein modifier of some sort and does not make the dogs different in terms of color genetics. They are the same thing
- Black and tan, designated a^t. It’s VERY important to understand what black and tan is. People assume, and want to believe, that it’s a black dog with tan markings laid over it. This has led to all kinds of statements, and even AKC standards, that call for a black dog with certain additional tan markings. What is actually happening with those dogs, though, is that they are sables in which the red pigment – the phaeomelanin – is only on the edges of the body. Think of it as being a bit like dropping a bit of dish soap in the center of a bowl of oily water. The oil immediately leaves the middle of the water and leaps to the edge and builds up there. A black and tan dog is a sable/red dog on which the red is prevented from showing up in certain places, NOT a black dog with additional red. Sometimes the genetic action that shoves the red to the edges is very strong, and sometimes it’s weaker. A weak action leaves very large red borders (as in saddle-marked dogs, where the “points” take up most of the body) or removes the red poorly (as in black dogs with lots of cinnamon or red at the base when you part the hair). However, those dogs are still genetically black and tan; they are not “bad” black and tans. And, dispelling another myth, the amount of red in a black and tan coat does not show the dog’s parentage (those with one red/sable parent don’t have more red, etc.)
- Recessive black, designated a. Recessive black is the all-over black of German Shepherds and Pulis and bi-black Shelties. Dogs have two flavors of all-over black – one is a dominant black (so a black dog can carry brindle or sable/red) and one is a recessive black (so in those breeds the brindles or the sable/reds carry black). Thankfully – at least as far as I know – there aren’t breeds that have both dominant black and recessive black. You just have to know which kind your breed has. Cardigans don’t have this gene, as far as we know.
II) The “B” locus (B is for black/brown)
- All eumelanin on the dog is black, designated B. This is the normal and dominant gene, and allows the dog to make black pigment.
- All eumelanin on the dog is brown, designated b. This changes all black pigment to brown pigment (NOT “red” or tan pigment, but chocolate brown). There are actually a bunch of b mutations but they all do the same thing and so most people just say “b.” All brown/liver/chocolate dogs are homozygous bb at this locus. Dogs who are bb cannot make any black pigment at all. All dogs with any black pigment at all, anywhere on their body, even if parts of their coat look kind of chocolaty, are either homozygous BB or heterozygous Bb. The bb chocolate mutation also changes the color of the nails and eye leather and nose leather, to either a pinkish chocolate color or what is sometimes called “self” coloration – a dark flesh color. (Interestingly, something very much like the “b” mutation occurs in humans, causing African American skin tones to turn lighter and redder.)
III) The “D” locus (D is for Dilution)
- All melanin is fully saturated in small grains along the hair strand, designated D.
- The melanin occurs in large clumps along the hair strand, designated d. This clumping makes the hair lighter in color, and so the dog looks “blue.” The d dilution changes black dogs to blue, chocolate dogs to a light brown/grey, and red dogs to a dusty red. It affects both types of melanin, though it seems to affect the eumelanin much more than the phaeomelanin.
IV) The “E” locus (E is for Eumelanin, which is black pigment)
- Black pigment may cover the body, designated E. We used to think that this was “THE” black-dog gene. We now know that’s not the case, which is why there’s a “new” locus called K for blacK, but the E locus still functions in some dogs to make them black.
- Black pigment may cover the face, designated E^m. This is the black mask that’s common in all but the hound breeds.
- Black pigment may make an overlay on the body but leave lighter/creamier color on the belly, neck, legs, and face, designated E^g. The “g” is for grizzle, which is the color in Salukis that led to this gene being described. Grizzle is very similar to the “urajiro” in Shibas and the other spitz breeds (including, and this is interesting to corgi breeders, the Pems), and my personal bet is that we’ll find that these breeds are E^g as well. Right now we don’t know; research on this particular variation of color isn’t complete. Grizzle/urajiro can be confusing if you just look at it cosmetically, because on a black dog it “looks” like the dog is a wide black and tan (where the points are really big and soft instead of defined and small). On a sable dog it looks like the dog is trying to be a black and tan dog (I’ve seen people assume that these lighter areas on the underside mean that the dog carries tricolor, for example). But this is NOT the black and tan gene (a^t, above)
- Black pigment may be entirely prevented from occurring on the body, designated e. Dogs that are ee are always a red, cream, or white color; they cannot have any black hairs anywhere. This is very common across the dog world; ee reds are found in a huge number of breeds. All Viszlas are ee reds, as are all Irish Setters, yellow Labs, Golden Retrievers, red/apricot/cream/white Poodles, and so on. “Pink” Cardigans are ee reds. As with the chocolate gene we looked at earlier, if even a single hair on the dog is black it is NOT an ee red.
V) The “G” locus (G is for Greying)
- G is a postulated locus (we know it’s there but have not yet mapped it), designated G for graying. It’s the gene that turns silver poodles from black at birth to nearly white in age, and is also seen in Kerry Blues, a bunch of the terriers, and in many of the breeds that lighten progressively as they age (like Great Pyrenees and Lowchen). In other words, it’s probably a lot more common than we think. Greying seems to be dominant to non-greying, and it occurs no matter what other colors are present on the dog. Interestingly, if a dog has a black mask and the G gene, the rest of the dog will grey and the mask will stay black for years longer than the body.
VI) The “I” locus (I is for Intense)
- I is another postulated locus (we’re pretty sure it’s there but are not exactly sure how it works) that has come to encapsulate what geneticists used to call “Chinchilla” or the C locus. It’s no longer called C because C is reserved for a type of severe dilution that causes genuine albino coloration, and it turns out that what we see in dogs is not a form of albinism but a form of diluting or washing out of the red pigment (phaeomelanin) but not the black pigment (eumelanin). The “Intensity” effect seems to be cumulative – that is, it may repeat itself and become stronger. If that turns out to be true, then one copy of the “I” gene changes a dog from, say, red to apricot, two copies will change a dog from red to cream and three copies will change a dog from red to white. The “I” effect is what creates most of the dog breeds who are white but retain black or dark nose leather, skin, and eyes. This includes white poodles, white German Shepherds, Samoyeds, and so on. I also dilutes red to apricot in Poodles and Vallhunds and Tervuren (“red” and “grey” Vallhunds and Tervs are actually sable and apricot sable). The I gene is very widespread and probably occurs relatively unnoticed in many breeds where the deepness of the red coloration is not paid much attention to.
VII) The “K” locus (K is for blacK). The K locus works with the A and E loci to result in various degrees of black and red pigment.
- The dog is black all over, designated K. This is the “dominant black” present in Danes and Labs and in a huge number of other breeds. Because the black is dominant, the dog could be homozygous black (KK) or heterozygous black (Kk^br – black carrying brindle; or Kk^y – black carrying some sort of red/yellow like black and tan or fawn/sable).
- The dog is brindle, designated k^br. The black is allowed to be expressed in a series of stripes or chevrons on the dog. The color of the coat under the striping depends on the E and A loci.
- The dog is not black all over, designated k^y. What the dog actually ends up looking like depends at this point on the E and A loci; it could be fawn/sable, black and tan, etc. Because k^y is recessive to k^br, you can have a homozygous brindle or a brindle carrying k^y.
VIII) The “M” locus (M is for Merle)
- The merle action is absent, designated mm. Whatever the dog is going to look like, he looks like.
- The dog has a defect in its production of melanosomes that renders some of them ineffective, designated Mm. Where the defective melanosomes end up on the skin of the developing embryo, the dog’s eumelanin will be less visible. Where normal ones end up on the skin, the dog’s eumelanin will be normal looking. These patches of normal and defective melanosomes create the characteristic pattern of a merle dog.
- The dog has a widespread destruction of its melanosome production, which leads to a coat that’s largely white – designated MM. Unfortunately, those same cells also are the ones that allow a dog to hear (the pigment cells in your inner ear are what tell your nerves to fire, which is what we interpret as sound) and also form some of the eye structures, so a dog with a drastically reduced number of healthy melanosomes is often deaf and may also have eye issues. The harm done to the dog seems to vary by breed, interestingly – Catahoula Leopard Dogs are often MM but are rarely deaf, while MM Danes are virtually always deaf and often blind. At least anecdotally, MM Cardigans are often deaf and may have eye issues but there are some individuals with neither problem.
- To really address spotting would take a book in itself. The short story is that we used to think that all white spotting on dogs was part of the “S” locus, but now we know that there are multiple gene actions that produce spotted dogs and everybody is kind of back to the drawing table trying to figure out exactly which actions apply to which breeds and when.
You can’t tell just by looking at a dog which spotting gene is at work, because they all function the same way. Pigment cells travel over the developing embryonic body almost like frosting is drizzled over a bundt cake – beginning at the top of the head, down the topline, and then spreading down the body of the dog and ending at the feet and the chest and midline of the stomach.
Anything that stops the progression of those pigment cells creates a white spot, and because of the way the pigment cells move the spots always begin on the feet and chest and tailtip. Then as the action of whatever gene it is strengthens the dog becomes white around the neck, then has breaks in the body color, then begins to lose the body color entirely, then loses the head color.
The different spotting genes seem to have varying degrees of predictability, too – in some breeds, like Cardigans, you can “fix” a spotting pattern relatively easily and have most of your puppies with very similar white. In other breeds, like Boxers, the spotting pattern is created by a different genetic action and so their markings swing wildly from zero white to entirely white dogs in the same litter.
There isn’t a designation yet for the kind of white spotting we have in Cardigans and other herding dogs. We know it’s not a form of piebaldism and we know that it is common in herding dogs and not terribly common in the other groups. It’s predictable and breeds true. For lack of a better word, I call it “herding spotted.”
Cardigans ALSO have the piebald gene, which is what creates breaks in our blanket colors, gives a lot of tail white, and causes the white markings that go up high on back legs. We don’t know exactly how the piebald gene or gene group works, though, and how it combines with other spotting patterns, because in some breeds it seems that when two piebald carriers are bred you get dogs that have massive amounts of white (that’s the way collies work, where two dogs with stifle white can produce color-headed whites), where in other breeds piebald carriers produce only a little more white than before. In my own breeding, I paired two Cardigans with very high stifle white and big fat tailtips and I got some small breaks in the blankets and some white coming up the sides of the puppies (they were clearly showing the effects of the piebald genes meeting) but I got no splashes or spots. So we honestly just don’t know a ton about it in Cardigans.
Until we have a more encyclopedic knowledge of the spotting genes it’s difficult to use them to breed carefully, except for this (which all breeders should understand): Every puppy gets color that bundt-cake way. There are no exceptions. And sometimes things happen embryonically that prevent the color from migrating fully down over the body, leaving a solid-colored puppy with white toes and a small white chest spot. These puppies are NOT genetically spotted. They are genetically solid with a little glitch in the color migration. They are not evidence of cross-breeding with a spotted dog, they are not scary, and most of the time they won’t reproduce those spots.
- Ticking has not yet been given a locus name, as far as I know, but it is very definitely a genetic phenomenon and is dominant to non-ticking (in other words, at least one parent must be ticked to produce a ticked puppy). Ticking is coloration that fills in as small spots or flecks within the white-spotted areas of a dog. It only appears within white spots. Heavy ticking is called roaning, and is found in English Cockers and Australian Cattle Dogs and others. Light ticking is found throughout the dog world. Some people think that ticking is always black, but that’s not true. The dog will tick in whatever color the white spot has deleted – so if the dog is tan or red, or the white spot covers a place that is cream or blue or whatever, the ticking will reveal that color and not black.
XI) Merle modifier: Harlequin
- The dog is a black and mouse grey merle, designated hh.
- The dog is a harlequin, designated Hh. The harlequin pattern is not really a gene but instead a particular protein encoder that tells the body to not fill in the areas that would be mouse-grey in a merle. As a result, the dog is white and black.
- The dog is a homozygous harlequin, designated HH. No living HH dogs have been found, leading to a conclusion that H is an embryonic lethal.
Continued in part 3.