DNA testing: What's your dog made of?

For centuries, dog lovers have been asking their pooches to sit and stay. These days, more owners are adding: Who's your daddy?

The increasing options to administer DNA tests for dogs (and to a lesser extent, cats) answers the call of curiosity, sure, but the tests that reveal your mutt's family tree also can help vets better diagnose disease and manage lifestyle issues like exercise, diet, and behavior problems.

At the very least, the tests - now more accurate than the ones first introduced to consumers about eight years ago - allow owners to know how big the dog they adopted at six months likely will be at six years.

The proof is in the pet-care company sales: Mars Veterinary, the dominant manufacturer among a handful of companies that produce consumer tests, sells the kits under the Wisdom Panel brand. Mars initially began offering the kits through veterinary offices in 2007, but once it went direct to consumers in 2010, sales doubled year over year, said Juli Warner, senior brand manager. So far the company - which can identify more than 250 breeds of about 400 with its $85 version by tracking genetic markers in the cheek cells of pets - has run about 400,000 tests, she said.

For Rich DiSipio, the tests set the record straight after the shelter where he rescued his dog Elvis told him the 4-year-old was a coonhound mix. His Canine Heritage Breed Test showed he is redbone coonhound and Clumber spaniel. Then, when the Washington Square resident added Franklin to the family a year later, he had him tested, too: German shepherd, Rhodesian ridgeback, and mixed hound.

"I think getting the DNA test makes you feel more attached to your dog - he's not just a mutt or a mix," DiSipio said.

He used the information practically, too. When Franklin was adopted at six months, he weighed 30 pounds. Based on his breed, DiSipio realized the dog had a lot of growing to do. Now 31/2, he weighs 50 pounds. "A lot of dogs have severe health problems - like a lab can have chronic hip problems," DiSipio said. "If they were part lab, I probably wouldn't let them jump so much."

This is how the kits work: Swab the dog's mouth twice between the cheek and the gum - you're not collecting saliva, but skin cells - for a total of 15 seconds. Let the swabs dry, register the kit online, and mail the swabs back.

Mars' breed identification kits also show whether the pet carries a mutation on the MDR1 gene, important in drug absorption and distribution to the brain. (Other test brands run as little as $60 without the MDR1 gene analysis.) In two to three weeks, you will receive a predicted weight profile, and your dog's family tree dating back to the great-grandparent level.

Urs Giger, a geneticist and professor at the University of Pennsylvania's School of Veterinary Medicine, said earlier tests could determine the composition of a mixed-breed dog, therefore predicting the approximate size and temperament of the dog, as well as activity level he or she might need. But the latest tests, which he called "revolutionary," can point out many hereditary diseases for which the pet might be at risk.

DNA results also can help behaviorally. "Trying to train a dog that has terrier in it like a retriever could be a losing battle," Warner said. "Dogs were bred for jobs and to really understand those gives a deeper bond with your dog."

With more manufacturers offering breed-specific foods and treats, added Matt Byrnes of PetSmart, the DNA tests could help owners better understand their pets' nutritional needs. Sales of DNA tests at PetSmart (the company carries Wisdom Panel) have doubled since it first started offering them. "We typically see a spike over the holidays," Byrnes said.

While many people would like to know their dog's breed before adopting, few shelters are able to afford the process.

"We dedicate funds to medical care for the animals but wouldn't be against using a DNA test if it was affordable," said Grace Kelly Herbert, president of Finding Shelter Animal Rescue, a foster-based organization out of Norristown. But she prefers people focus on the dog's behavior, anyway. "We try to educate people that who a dog is is more important than what they are. If people focused less on the look of a dog and instead considered their qualities as a future family member, more mixed-breed dogs would find homes more easily."

When Kate Patrizzi, of Voorhees, adopted her dog three years ago, the shelter told her he was a Jack Russell/Chihuahua mix. Already 2 years old and fully grown, he didn't resemble either of those breeds. Her vet thought he was a basenji/corgi mix, and people on the street had their own theories. So a year and a half ago, Patrizzi bought the Wisdom Panel DNA test.

"When I got the results, I remember thinking, what if he's something that people in society think is a violent animal?" she recalled. "It said he was part Akita, part German shepherd, part Chinese Shar-Pei, and part rat terrier. I was totally surprised."

Patrizzi was skeptical - three of the four are large dogs and hers weighs 25 pounds. But bewildering results are possible: Breeds that are very different in appearance sometimes have similar genetic signatures.

Lisa Harwood, a vet at Companion Pet Hospital in South Philadelphia, has helped clients with DNA tests over the last five years (blood tests from vets cost between $120 to $250). But she isn't sold on the accuracy of the science.

"The idea is intriguing and interesting, and the information that could be gained in theory can be really valuable," she said. "But I'm not sure there's enough consistency and accuracy at this point that would help me to make medical decisions in treating an individual patient. In most cases, pet owners can do them cheaper and more easily on their own."