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Can DNA Decipher the Mix?

How They Do It
Sue DeNise, vice president of genomic research at MMI Genomics Inc., which developed the Canine Heritage Breed Test specifically for mixed-breed analysis, talked to us about how her company analyzes canine DNA. “We’ve been doing testing for AKC parentage verification for a long time,” she notes. “We initially started working in the cattle business, looking for genetic markers in order to trace what was important to cattle breeders. Out of that whole-genome association study, we had purebred and crossbred cattle, so we asked, ‘What can the markers tell us about underlying traits in breeds of cattle?’” Their discovery paved the way for the companion animal program, which was modeled on what they learned with cattle.

“We look at ’breedness‘ among dogs. Our canine database is built with 10,000 samples of 108 breeds. We ran 400 markers to identify the best markers for a ’breedness‘ test against 38 breeds. We created a panel of 96 pieces of DNA that split dogs into their identified pure breed. In our preliminary test, we found that individual purebred dogs cluster with other purebreds.” Initially, MMI chose 38 AKC registered breeds from their database, selected for their popularity based on number of registrations. Recently, as DeNise notes, they increased the number to 108 breeds. This jump in breed recognition required testing thousands of markers to identify the just over 300 markers that characterize these 108 breeds.

Constructing Breeds
Like all species, domestic dogs are on an evolutionary journey, starting at wolf and going somewhere yet to be determined. We tinker with evolution, but might be surprised to find out we don’t control it. Our concept of a breed—that individuals within the breed look alike—is nothing more than a snapshot of the DNA time line, taken while we’re doing the tinkering.

Breeds are created a number of ways. In simple terms, when breeders interfere with natural reproduction and rigorously select for traits favored by humans, specialized breeds like Retrievers, Spaniels, Hounds and Terriers are the result. Saving spontaneous mutations in a litter of dogs, repeating the breeding to get more of the same mutation, and breeding those dogs back to one another has resulted in the English Bulldog, Chinese Crested and Inca Hairless. More recent breeds, such as the Airedale, Australian Cattle Dog and Doberman, are the result of crossing older breeds to make new ones.

When kennel clubs closed gene pools in the late 19th century to suspend change in registered dogs, breeds drifted toward a more uniform stereotype. Until the early 1800s, an assortment of dogs with similar talents who could produce somewhat similar offspring were awarded the right be called a breed. Breeds evolved, flourished and disappeared when jobs were eliminated. Tumblers, who mesmerized prey by “winding their bodies about circularly, and then fiercely and violently venturing on the beast,” disappeared when guns came into widespread use. Turnspit dogs, who made a living running on a wheel to turn meat so it would cook evenly, received their pink slips when technology improved cooking methods.

By and large, Victorian society was not so pragmatic; sentimentality and commercial opportunity were catalysts for saving unemployed breeds from their inevitable demise. As a result, many Terrier breeds went from killing varmints in the barnyard to killing time in the Victorian parlor in less than a decade.

Whereas previously, a breed was a regional product maintained and preserved by a small community of knowledgeable people, commercial interest in the well-bred pet dog initiated a shift in breeding practices during the Victorian era. The old-money kennels operated as a pastime by the wealthy gave way to a large number of small, commercially operated kennels run by entrepreneurs of modest means and experience.

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