She’s such a delightful dog, and you were lucky to find her at the shelter that day. But what exactly is she? Her cheese-curl tail evokes a shiba inu. Those droopy ears are all spaniel. And only a schnauzer could have gifted her those magnificent eyebrows. Everyone who meets her spots another breed in the hodgepodge.
Thanks to the miracle of DNA testing, you don’t need to guess anymore. Or, at least, that’s the pitch. You can just buy these kits online. You swab around your dog’s mouth, drop it in the post and you’re sent a precise numerical breakdown of everything she is and isn’t. But is it true?
It may surprise you to hear that, yes, it is actually true. Or at least the basic science of it is. These tests work by screening for thousands of subtle genetic mutations (properly called single-nucleotide polymorphisms, or SNPs) that are statistically prevalent in particular breeds. I should emphasize that these SNPs aren’t otherwise important. They are not genes, and they are not directly responsible for any of the traits that define a breed. They are merely markers—unique chance errors that popped up long ago when these breeds were forged by human selection, and they have persisted in those lines to this day. They don’t do a whole lot, but if you find one, you can say with confidence that one dog is descended from another.
The question isn’t whether the theory is sound, but whether it works in practice. And I’m afraid this is where things get murky. In my own experience, the results are inconsistent, ranging from “well that makes perfect sense” to “seriously?” And that renders it a bit pointless. If the results fit our expectations, we pat ourselves on the back for being as clever as geneticists. If they don’t, we exchange skeptical glances and ponder the wasted money.
It’s not that the tests are nonsense. They’re legitimate, but the technology is still young. As databases swell with discoveries of new SNPs, and as statistical models are accordingly updated, we’ll certainly see accuracy improve.
If we imagine a day in the future where these tests are more reliable, would there finally be a use for them? It’s still unclear. Does it really help to know that your dog is 6 percent shih tzu and 17 percent saluki? The manufacturers say yes, contending that every breed has its list of common problems, and that forewarned is forearmed. But remember that these tests aren’t looking for functioning genes, which limits their predictive value regarding specific genetic abnormalities. I’m simply not convinced that they yield information that couldn’t be gleaned from an old-fashioned eyeballing. If it kind of looks like a boxer, it’s probably part boxer.
That’s not to say that other kinds of genetic testing don’t have their place. For example, collies frequently carry a mutation in a gene called MDR1 that alters the way their bodies process certain drugs. This information may affect my choices in caring for that patient. But I can easily test for that specific mutation, so there’s no need to agonize over what percent collie the dog is.
For the time being, DNA breed testing is more of a novelty than a useful medical diagnostic. And that’s completely fine. There’s nothing wrong with having some fun with science, so long as people know what they’re buying. These kits can be interesting gifts for the mutt-lover in your life. But as a veterinarian, I expect it’ll be a long time before I start adding any of that information to my patients’ charts.
Dr. Mike Fietz is a small-animal veterinarian at Georgetown Veterinary Hospital. He received his veterinary degree from Cornell University in 2003 and has lived in Charlottesville since.
You can meet us at the Charlottesville-Albemarle SPCA, where we’re all available for adoption. 3355 Berkmar Dr. 973-5959, caspca.org, noon-6pm, daily COURTESY Charlottesville-Albemarle SPCA
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