- The Washington Times - Wednesday, March 23, 2005

Call them mongrels, mutts or mixed breeds. Just don’t assume dogs with less-than-perfect papers are genetically superior to their purebred peers.

Mixed-breed dogs may have acquired that “doggie urban myth” because hybrids tend to be superior in other areas, such as tomatoes, but animal experts say the study of dog genetics is an inexact science that makes few guarantees.

Lisa Peterson, manager of club communications with the New York-based American Kennel Club, says the wisdom behind the superior-mutt myth doesn’t hold up to scrutiny.

“Genetically speaking, you can have some purebred dogs that are more diverse genetically than mutts,” Ms. Peterson says.

That said, aninexperienced breeder who swims in the shallow end of the gene pool by inbreeding his or her prized dogs risks producing a genetically inferior pup.

“The more you line-breed or inbreed, the smaller the gene pool becomes. More recessive genes come to the fore,” she says. “Responsible breeders don’t breed that way.”

Purebred dogs’ advantages include a predictability mutts can’t match.

“You know what the boxer puppy will look like as an adult. It doesn’t deviate that much,” Ms. Peterson says. With mongrel dogs, “you have no idea which genes will take over.”

Phil Sponenberg, professor of pathology and genetics with the Virginia-Maryland Regional College of Veterinary Medicine in Blacksburg, Va., says breeders can safely bet on just a few predictable traits emerging in mixed-breed dogs.

Changes often lean toward what Mr. Sponenberg calls “less specialized types,” such as a boxer’s stubby snout.

“You’re more likely to get something that looks like a generic dog,” he says.

Sometimes, dogs of different breeds are mated with such consistency that they evolve into a breed unto itself. The bull mastiff is one example of a breed that didn’t exist hundreds of years ago.

Various dog organizations disagree on just what qualifies as a new dog breed, but, Mr. Sponenberg says, generally speaking, a combination deserves to be called a breed when it can be mated consistently and yield dogs that appear very much like the parents.

Ms. Peterson says some recent combinations, what breeders often call “designer dogs,” may not strike a dog owner’s fancy as anticipated.

The labradoodle — a mix of Labrador retriever and poodle begun in the 1970s in Australia — is one of the more popular combinations because the dogs’ coats are said not to trigger allergies. It is, however, an example where the buyer should beware.

Some traits, such as nonallergenic coats like those of poodles, don’t manifest themselves until the dog is at least 2 years old, Ms. Peterson says. Also, not every labradoodle will have sneeze-free hair, a condition made possible by the dog’s low-shedding coat.

Breeders need multiple generations before their crossbred dogs have enough consistency to yield reliable traits.

Elaine Ostrander, chief of the cancer genetics branch at the National Institutes of Health’s National Human Genome Research Institute, says a key reason there’s so much interest in dog breeding is the sheer number of possibilities.

“Most dogs of any one breed can be crossed with dogs of any other breed,” says Ms. Ostrander, whose office is involved in mapping the canine genome. “There are exceptions, but dogs are all members of the same species. They have the same number of chromosomes.”

She says her organization partners with breeders and dog-show organizers to get a closer look at canines.

“Some of the best geneticists in the world today are ones who never had a genetics class but breed dogs,” she says. “It involves years and years of careful observations.”

Breeders help her understand how genes manifest themselves because they keep tight track of their dogs, their dogs’ siblings and the various diseases and conditions they incur.

“They’re really the genealogists. They do an extraordinary amount of legwork,” she says. “That gives us a huge amount of information [on] whether the underlying gene works in a dominant or recessive fashion.”

Studying dog genetics is important, she says, because dogs and humans share more conditions than one might suppose.

“They get all the same diseases we do,” she says, ticking off medical concerns such as cancer and epilepsy.

All that’s needed to glean genetic information is a swab gently raked across a dog’s inner cheek, she says.

That measure also could help dog owners one day find out which dog breeds are in their mongrel pets.

“Owners want to know what diseases are you looking out for,” she says. “If you’re a golden retriever [owner], you want to look out for lymphoma.”

Stephen L. Zawistowski, senior vice president of national programs and science adviser with the American Society for the Prevention of Cruelty to Animals in New York, says examining genes alone isn’t the best way to get to know man’s best friend.

Dog traits and behaviors depend on a combination of genotypes and the environment, he says, much like those who say humans are a composite of nature and nurture.

“Your best bet is to have a good genotype raised in the best possible environment for dogs,” Mr. Zawistowski says.

A key time for nurture to make its mark is during the dog’s early weeks, specifically between 3 and 16 weeks of age, he says. Regardless of a dog’s genetic background, it will be a better-socialized pet if exposed to society during that time, he says.

“It doesn’t mean you can’t take an older adult dog and be successful [with socializing],” he says.

Training also can help overcome ingrained activities, such as chasing predators.

“You’re always working within this combination of the genetics an individual [dog] comes with and the environment,” he says. “Different genotypes can react significantly different in different environments.”

Breeders often try their best guess when mating their animals.

“If you have a dog who is intensely aggressive or very, very fearful, you’ve got to think twice about breeding that particular dog,” he says. “Those are the types of traits you don’t want to perpetuate. You want to create the best possible odds for a good family pet.”

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