Obviously the ability to interbreed makes all dog breeds the same species (Get me a ladder! barked the Chihuahua next to the Great Dane in heat), but given the rapidity with which a breed can be developed and altered, how valid is DNA testing to determine breeds?
In Quebec a public argument is raging concerning dangerous dogs, with legislators taking action against pit bulls. On one side you’ve got people saying dogs known to kill people (as happened in Montreal in June) should be banned, and they don’t want to see pit bulls (American Staffordshires, Staffordshires, Pit bull terriers, and the like) in cities or the province.
On the other hand there are those who believe there is no such breed as pit bull, and who question whether it is actually pit bulls that maul and maim and kill or some other breed, since owners frequently register their dogs as boxers instead of pit bulls.
But that’s all sideshow. What I want to know is: given how easily dogs of all breeds can reproduce, and given the sheer number of mutts vs. purebreds, are there specific genetic markers that can distinguish between breeds, and can we test for them in a reliable fashion?
Well I assume you could test the mitochondrial and Y chromosome DNA and establish parentage. Then if Mommy and Daddy are pit bulls so is baby. But that just pushes the problem back one generation.
In any case, I’m not sure how you define it. Suppose for the sake of argument, you could establish that Mommy is a pit bull and Daddy is a poodle with 100% reliability, what does that mean puppy is?
The reality is that it doesn’t matter. The history of breed-specific legislation shows that over and over again, authorities on a witch hunt intentionally design the legislation to:
[ul]
[li]Affect “pit-bull type dogs and similar dogs”[/li][li]Often a wide variety of other breeds (German Shepherds, Chow-Chows, Rottweilers, Dobermans, etc.) and dogs who subjectively look like those breeds[/li][li]Permit (often entirely untrained) police officers to make that subjective determination whether a given canine meets these nebulous criteria[/li][li]Specifically disallow breed identification or testimony from a veterinarian[/li][/ul]
That last bullet point seems to be included because of fears that sympathetic vets will act to protect dogs they know pose little danger. So the laws are written to exclude the experts.
The fear seems to be that such laws are not casting a wide enough net.
It’s a with hunt, pure and simple. Never mind that breed prejudice is condemned by dog experts, the American Veterinary Medical Association, the American Bar Association, the Center for Disease Control, and most public shelters – such laws have repeatedly been shown not to work. Attacking the dogs is political grandstanding that makes one appear “tough on crime” without requiring serious thought or good police work.
Such laws may also be racist in intent – one recent book suggests that the association some people make between pit bulls and poor black communities makes it easier for them to ban “those people’s” dogs when they wouldn’t dream of a ban on their own communities.
What I’ve said above is, I feel, germane to the intent of your question – the authors of these laws are not interested in, and may in fact be intellectually opposed to, accurate identification of breed, genetically or otherwise. Because the laws aren’t intended to promote public safety; they only masquerade as such.
DAN testing is pretty much useless. If your vet wants to make money off of it, they may tell you differently, but my vet, being honest, told me that if I wanted to do a DNA test to find the origins of my mutt, I would be better off using a dartboard.
Obviously, it can be used to prove parentage, if there is reason to believe that a dog is related to another particular dog, that can be proven or disprove, but as far as breed ID goes, it is useless.