FORT MOTT STATE PARK, N.J. — When mutant, muscle-bound puppies started showing up in litters of champion racing whippets, the breeders of the normally sleek dogs invited scientists to take DNA samples at race meets here and across the country. They hoped to find a genetic cause for the condition and a way to purge it from the breed.
It worked. "Bully whippets," as the heavyset dogs are known, turn out to have a genetic mutation that enhances muscle development. And breeders may not want to eliminate the "bully" gene after all. The scientists found that the same mutation that pumps up some whippets makes others among the fastest dogs on the track.
With a DNA screening test on the way, "We’re going to keep the speed and lose the bullies," Helena James, a whippet breeder in Vancouver, British Columbia, said.
Free of most of the ethical concerns — and practical difficulties — associated with the practice of eugenics in humans, dog breeders are seizing on new genetic research to exert dominion over the canine gene pool. Companies with names like Vetgen and Healthgene have begun offering dozens of DNA tests to tailor the way dogs look, improve their health and, perhaps soon, enhance their athletic performance.
But as dog breeders apply scientific precision to their age-old art, they find that the quest for genetic perfection comes with unforeseen consequences. And with DNA tests on their way for humans, the lessons of interveningin the nature of dogs may ultimately bear as much on us as on our best friends.
"We’re on the verge of a real radical shift in the way we apply genetics in our society," said Mark Neff, associate director of the veterinary genetics laboratory at the University of California, Davis. "It’s better to be first confronted with some of these issues when they concern ourpets than when they concern us."
Some Labrador breeders are using DNA tests for coat color to guarantee exotic silver-coated retrievers. Mastiff breeders test for shaggy fu rto avoid "fluffies," the long-haired whelps occasionally born to short-haired parents.
Next up, geneticists say, could be tests for big dogs, small dogs, curly-tailed dogs, dogs with the keenest senses of smell and dogs that cock their heads endearingly when they look at you.
Scientists who recently completed the first map of a dog genome (of a boxer named Tasha) are now soliciting samples from dog owners across theworld to uncover the genetic basis for a slew of other traits.
Some discoveries grow out of government-financed research aimed at improving human health. Others are paid for by breed clubs carrying out their mission to better their breeds. By screening their dogs’ DNA for desirable and undesirable traits that might appear in their offspring, breeders can make more informed decisions about which dogs to — or not to — mate.
But because genes are often tied to multiple traits, scientists warn, deliberate selection of certain ones can backfire. The gene responsible for those silver-coated Labradors, for example, is tied to skin problems.
With the genetic curtain lifted, breeders also take on a heavier burden for the consequences of their choices. Whippet breeders who continue to mate fast dogs with one another, for instance, now do so knowing they may have to destroy the unwelcome bullies such pairings often produce.
Moreover, the prospect of races being won by dogs intentionally bred to have a genetic advantage may bring new attention to the way that genes contribute to canine — and human — achievement, even when the genetic deck is not stacked. Inborn abilities once attributed to something rather mystical seem to lose a certain standing when connected to specific genes.
A mutation similar to the one that makes some whippets faster also exists in humans: a sliver of genetic code that regulates muscle development, is missing.
"It would be extremely interesting to do tests on the track finalists at the Olympics," said Elaine Ostrander, the scientist at the National Institutes of Health who discovered that the fastest whippets had a single defective copy of the myostatin gene, while "bullies" had two.
"But we wouldn’t know what to do with the information," Ms. Ostrander said. "Are we going to segregate the athletes who have the mutation to run separately?" For the moment, it is whippet owners who find themselves on the edge of that particular bio ethical frontier.
It was not exactly news to breeders that speed is an inherited trait: whippets were developed in the late 1800s specifically for racing. But knowing that one of her dogs was sired by a carrier of the gene, said Jen Jensen, a whippet owner in Fair Oaks, Calif., makes its championships seem "less earned." Ms. Jensen’s suggestion that a DNA test be required for all dogs and that the fastest ones without the mutation be judged and raced separately, however, has not gone over well.
At a recent race here in southern New Jersey, some whippet owners wanted the mutation eliminated altogether, even if that meant fewer fast dogs. But as the dogs pounded after a lure at 35 miles per hour, several owners allowed that they would prefer a whippet with the gene for speed.
"It’s more fun having fast dogs than slow dogs," said Libby Kirchner,of Glassboro, N.J.
The headaches are enough to make some breeders long for the time when decisions about breeding were dominated by intuition and pedigree charts. Selecting a mate, they say, was meant to involve mystery — in any species.
"It makes it so there’s no creative expression," said Cheryl Shomo, of Chesapeake, Va. "Now everyone’s just going to do the obvious thing."
Even so, many veteran breeders welcome the transparency the tests confer. Because while like tends to beget like, it doesn’t always work that way.
Mary-Jo Winters, a poodle breeder, uses a DNA coat-color test to ensure there are no genes for brown fur lurking beneath her black-and-cream-colored dogs.
"I don’t want brown," said Ms. Winters. "It’s not my thing."
Judy Pritchard, a Doberman breeder in Toledo, Wash., screens dogs she is considering breeding for a gene responsible for von Willibrand disease, a bleeding disease like hemophilia that also affects humans.
DNA tests, Ms. Pritchard said, "are the greatest tools that have been offered to dog breeders since the beginning of dogs. You need to use them to improve the breed."
Many breeders hope this new effort to corral nature will weed out the numerous recessive diseases that plague purebred dogs after generations of human-imposed inbreeding. But some question the wisdom of escalating intervention. Mark Derr, an author who has written about the history of dog breeding, urges everyone to reconsider the goal of genetic purity.
"I always use dogs as the example of why we don’t want to be mucking around with our own genome," Mr. Derr said. "These people are trying to use DNA tests to solve problems of their own making."
Still, some proponents of using the DNA palette are proposing to go even further. Dr. Neff, the University of California researcher, has proposed screening successive generations of dogs with DNA tests and breeding only those with genes for traits like stamina and scent detection to create a new breed of dogs to patrol subways and airports. It could be done within a few years, he said, instead of the centuries it took shepherds to breed the sheepdogs that patrol their flocks.
Even those who want to exert more direct control over dog DNA, however, agree that no genetic test can predict the intangible qualities that make a dog great.
If a dog does not have the spirit to run a race, it is not going to win, said Betsy Browder, a whippet owner in College Station, Tex.
"'Keenness' is what we call it," she said. "Just like you can have a human athlete who’s really lazy, and all the genes in the world aren’t going to help."