Curiosity is a great motivator, but my curiosity about Rascals breed mix would have come to nothing had I not submitted to a DNA test myself shortly before we adopted him. I wasnt looking for my own genetic ancestry; Im wary of what such tests reveal and warier still of how their results might be used. Commercial DNA testing has revealed family secrets, solved crimes long consigned to the cold-case files, even affected census results.

From human genetics research particularly studies involving identical twins we know that DNA influences much of what we consider to be our most human traits: our personality, our preferences, our I.Q. Lay people, even many researchers themselves, tend to find such research troubling, hinting at a kind of genetic determination.

Despite the unresolved ethical and cultural issues raised by DNA testing, its potential medical benefits are remarkable. I have a rare inherited syndrome that almost certainly killed my paternal grandmother at 51 and accounted for my fathers cancer diagnosis in middle age. When I submitted a saliva sample to a medical lab for genetic testing, I was contributing to research that might identify the gene that causes the condition, saving future patients from the expensive and disruptive cancer screenings that I undergo every year.

All of which primed me to reconsider DNA testing when we adopted Rascal; canine DNA tests can also reveal certain inherited medical conditions. In January, our rescue dog Millie died of complications of epilepsy. If Rascal carries a genetic risk for something terrible but treatable, too, I wanted to know about it.

Following a recommendation from Wirecutter, which evaluated 17 DNA tests on the commercial market, I ordered one from Embark and sent in a sample of Rascals saliva. A couple of weeks later, I got his results: 35.9 percent Chihuahua, 34.4 percent poodle, 6.9 percent bichon fris and 22.8 percent supermutt, Embarks catchall term for trace amounts of DNA from distant ancestors. Rascals ancestors apparently include a collie, a Pekingese, a Shih Tzu and a Maltese terrier.

The test also revealed that Rascal carries two copies of a gene variant associated with disk disease. Even before the breed results arrived, I got an email from one of Embarks veterinary geneticists explaining the risks associated with this variant and recommending some mitigation strategies. Some of them, like using a harness on walks, were easy to do. Others, like discouraging jumping, were less so. Keeping this buoyant little dog earthbound is a fools errand, but I was extremely grateful for the detailed advice.

Breed mix remains a matter of indifference to me. What does it mean that my gentle granddog has a wolf somewhere deep within her lineage? Apparently nothing. Thats the mystery of individuality, even in dogs.

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Opinion | What I Learned Testing My Dogs DNA - The New York Times