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Decoding the secret lives of dogs

DNA testing for disease, pedigree can also unravel a mutt's makeup

June 24, 2007|Karen Kaplan | Times Staff Writer

The Wilson family had puzzled over their mutt Drake's distinctive behavior ever since they brought him home from the Washington Animal Rescue League four years ago.

Workers at the shelter told them the dog was a mix of spaniel and Plott hound. But his propensity to leap over 4-foot fences and herd family members as if they were livestock had them thinking border collie.

The answer to Drake's past came in the form of a $65 DNA test that promised to scour his genes for telltale signs of the breeds in his family tree. "We were always curious as to what breeds went together to create him," Marcy Wilson said. "We just assumed we could never find out."

Not long ago, genetic testing was a rarefied pursuit used primarily to settle paternity suits, diagnose medical conditions and identify rapists and killers.

Now DNA testing has gone to the dogs. With sequencing technology becoming less expensive, dog owners are having their pets tested -- and sometimes finding that unraveling the mysteries of their genetic code can be a mixed blessing.

For less money than a luxury shampoo and doggy massage, owners of Canis familiaris can uncover their pooch's ancestry or take an inventory of its constituent breeds. The tests can also reveal debilitating health problems and other genetic surprises.

"If you're an animal lover, you can't resist this," said Jan Lovelady, a nurse administrator in Gilbert, Ariz., who had her mutt's DNA analyzed to see which breeds were in his lineage.

Half a dozen or so dog DNA analysis companies have sprouted across the country and peddle their services at dog shows and over the Internet. The firms guard their sales figures closely, but each claims to have tested several hundred to several thousand dogs.

The DNA of 400,000 purebred dams and sires has been registered with the American Kennel Club, which has required breeders to submit genetic samples since 1998.

But the rush to genetically type man's best friends has raised many of the same concerns as the typing of man himself.

"It's one more way of codifying the American cultural belief in genes as the foundation of everything important," said Donna Haraway, a historian of science and culture at UC Santa Cruz. "I find it mildly disgusting."

Then again, as the proud owner of two dogs, she added: "I might actually buy such a test."

Dog DNA tests generally fall into three categories: proof of maternity or paternity, genealogy, and identification of mutations associated with disease. Genetic tests are available for other animals -- to determine the sex of birds, for instance, or the coat color that cats may pass to their kittens.

Far more can be gleaned about dogs because of their use in medical research for human diseases, including cancer, heart disease, blindness, epilepsy and diabetes. The complete dog genome was published in 2005, making it the fifth mammalian genome decoded, after humans, mice, rats and chimpanzees.

The earliest consumer tests stemmed from the American Kennel Club's attempts to ensure the validity of pedigrees for 155 breeds of dogs.

As it turned out, the DNA evidence cast a shadow on the scrupulous record-keeping that is the hallmark of elite purebreds.

When the policy was implemented nine years ago, random inspections found that 13% of puppies had the wrong parents listed on their pedigrees, said club spokeswoman Lisa Peterson.

Some of those cases involved legitimate mix-ups, because puppies in the same litter can have different fathers. But there were also cases that involved unscrupulous breeders falsifying information on a pedigree to boost the puppy's value.

"Whenever there's a question about the parents, it raises questions about the integrity of the breeder," said Randall Smith, manager for DDC Veterinary, a Fairfield, Ohio, company that tests tens of thousands of animal DNA samples each year.

Today, the pedigree error rate has dropped to about 4%, according to the AKC.

Genetic tests have proven a powerful tool for breeders to continue shaping the evolution of dogs, which began more than 15,000 years ago when a few curious wolves ventured into ancient human encampments. Selecting for desired traits like docility and obedience, prehistoric people domesticated those animals and created a new species.

But hundreds of years of inbreeding to create modern purebred dogs has come at a cost. Certain breeds have persistent genetic problems cemented into their DNA. A crippling joint ailment known as hip dysplasia, for instance, is common among German shepherds, Labrador retrievers, Rottweilers and other large dogs.

Joan Bendure, who breeds Portuguese water dogs in Fairview, Pa., became interested in canine genetics when two of her dogs were diagnosed with progressive retinal atrophy, a disease that attacks peripheral and nighttime vision before leading to blindness.

The disease "destroyed a lot of kennels," she said. "For me, it took four dogs out of the breeding pool and left me with one."

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