Understanding coat color (and inheritance) in the Cardigan Welsh Corgi
Because the Cardigan has a history shared with a broad range of dog types – the teckel (primitive dachshund, accessing the hound genes), the herding dogs (accessing those genes, especially the recessive black), and even the spitz dogs (accessing certain dilution genes), we have the possibility of creating in our breed a whole bunch of colors. It’s like a playground for those who love color genetics, like I do, but unfortunately that possibility, and the associated “surprises” that sometimes pop up in litters, has made many breeders very afraid of what might happen when colors are bred together. There’s a feeling, which I think is quite incorrect, that the better breeders are the ones that do the very tightest range of breedings, and so to be a good breeder you need to stick within a very few possible breedings and possible colors lest you end up with what people call “bad” color.
My goal is not to tell you which breedings to do. It’s to show you that color breeding is one of the few things in dog breeding that we really can understand, get a grasp on, and control. It can feel very mysterious to a new breeder, and even to some experienced ones, but it’s actually very predictable and should never be scary.
Here are the things you need to know:
1) Colors are proteins, not paint.
Since the beginning of organized breeding, breeders have been tempted to think of coat color as though it can be mixed and swirled. Need a lighter color? Breed to a lighter dog. Need a darker one? Find yourself a black dog. This has led to all kinds of bizarre recommendations, old wives’ tales, and perfectly good dogs being discarded because they showed “evidence” of an unwanted color.
It’s completely wrong and we’ve got to stop. The color genes code for particular proteins that, when they work in concert with all the zillions of other proteins in the body, create a color on the outside of the dog.
The color genes are much more like a deck of cards than they are like paint. There are some major divisions (think of them like the face cards and number cards) and within each division there are a number of choices (think of the suits).
When all the cards are put together, they combine to form powerful units that tell the dog’s developing body where to put color cells and what proteins those color cells are allowed to produce.
But, in the same way that a full house usually beats a pair of twos, but make that pair into four of the same card and it beats the full house, the cards themselves don’t have the power. The combination does. And, in the same way that handing a two of clubs to one player may give him a straight flush, but handing the same card to another player gives her two of a kind, the contributions of each parent dog may result in a whole ton of different colors in the babies – sometimes dramatically different cosmetically than either parent.
2) Proteins are never just about color.
The genes that affect color are not just inkjet printers. That’s been the number-one discovery about color this century, and has turned a lot of color genetics on its head (and made things very exciting). As it turns out, the colors appear the way they do because the gene introduces defects into certain proteins. Most of the defective proteins don’t do anything bad to the dog, but a few of them are actually harmful – for example, it now seems relatively certain that the gene that turns Dalmatians from ticked dogs (with lots of little round specks) to Dalmatians (with a few big round dots) is the same gene that makes them unable to break down uric acid properly.
We’re also discovering that certain things we thought were simple are not so simple at all. I am sure you’ve heard that if you’ve got a big white blaze you run the risk of getting a blue eye. We want to intuitively understand this like it’s paint – paint white over the eye and it turns blue. But in fact it’s much more likely that the same proteins that prevent pigment from being expressed on the skin affect the way in which the eye develops. What we’re seeing is not causation – the white blaze doesn’t cause the blue eye – but correlation – same protein affects both skin and eye.
We’ve got to get our brains around this because the next few decades are going to see an explosion of new knowledge and we’re going to have to make ethical decisions based on that knowledge. What if we find that (and I’m just making this up, but it’s not far-fetched) chocolate-pigmented dogs are forty percent more likely to have thyroid problems than black-pigmented dogs? Or that (and this one I’m not making up) it may be that all merle dogs are at risk of hearing loss? We’re going to have to address that new information, and to do so we need to understand it.
Continued in Part 2.