Sanda Lambert stood with her daughters and husband in the kitchen of their DC home last July in a state of disbelief. She had just opened a letter from MetaMorphix, a Calverton biotech company that uses DNA testing to determine the breed composition of dogs.

The Lamberts had thought that Minnie, their dog of more than five years, was a Chihuahua mix; that’s what the Washington Animal Rescue League had labeled the two-month-old pup when the Lamberts adopted her. Every veterinarian that had examined Minnie had identified her that way. According to MetaMorphix’s Canine Heritage Breed Test, she’s not even 1 percent Chihuahua.

“I had to send out an e-mail to all our friends and neighbors saying we were wrong,” says Lambert.

MetaMorphix introduced its canine DNA test in 2007 as the first of its kind. Since then, competitors have popped up. Most vets agree that DNA testing for dogs is not definitive, but that hasn’t turned away curious pet owners.

To determine a mutt’s makeup, the Heritage test examines its genotype and finds the best matches among more than 100 breeds’ genetic structures. The mail-in test, which costs $99.95, uses a cheek swab to collect the DNA. The results come back in four to six weeks, with the detected breeds grouped by levels of importance.

Minnie didn’t have a primary breed listed. Most mutts don’t. “Primary breed” would mean that one of her parents was most likely a purebred; in any case, MetaMorphix says, a “primary breed” dog is at least 50 percent one breed. Instead, Minnie’s DNA-based description listed a secondary breed—one that’s detected at a significant level—which is dachshund, a short-legged hound. Also in the mix were small amounts of Cairn terrier, pug, and Pomeranian.

“My neighbors call her a Fauxhuahua now,” Lambert says.

She hopes the information will be useful if Minnie has health problems: The dog was previously diagnosed with a paralyzed larynx, a condition unusual for Chihuahuas. That was the reason Lambert had Minnie tested.

“In my experience, retrievers have a tendency for cancer and shepherds for hip dysplasia,” says Gary Weitzman, executive director of the Washington Animal Rescue League. “It doesn’t hurt to know. Down the road it may be something that is very useful.”

Another test is Mars Veterinary’s Wisdom Panel Mixed Breed Analysis. The $125-and-up test is more comprehensive than the Heritage test—it detects more than 150 breeds—but requires a vet to draw a blood sample.

Jeffery Newman, a veterinarian at Caring Hands Animal Hospital in Arlington, has collected ten such blood samples. “People put a lot of emphasis on breed, but you get misbehavior and problems in all breeds, just like you do with people,” he says. “It really comes down to the individual.”

People stop Jill Stepak on the sidewalk to ask about her dog, Toby. When she adopted Toby last February, the DC resident thought the dog might be a dachshund or corgi mix. She decided to swab his cheek—and it turns out he’s neither. Toby is a mix of Pomeranian, beagle, English toy spaniel, and miniature pinscher.

“It’s a lot to list,” she says. “He’s a mutt of a mutt of a mutt.”

This article first appeared in the March 2009 issue of The Washingtonian. For more articles from that issue, click here.