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Can DNA Decipher the Mix?

Germane to this tale is that, according to the unwritten rules governing canine physiology, anatomy and behavior go hand in hand. One cannot be changed without affecting the other. Victorian enthusiasts who were busily adding aesthetic traits to utilitarian breeds were creating not only subtle variations in type, but in many cases, modifications in behavior as well. As utilitarian breeds went from working hard to hardly working, many exhibited new physical and behavioral characteristics that were compatible with their augmented duties as companion animals. Breeders claimed the “sub-breeds” as their own, made up new names and registered each one.

However, no matter how they’re sliced and diced, reducing and suppressing genes so they aren’t expressed doesn’t mean they’ve been eliminated. They’re still lurking and, depending on the method used to analyze the DNA, the lurkers often show up in the results.

Deconstructing Breeds
The problematic aspect of analyzing mongrel DNA is that breeds were not all created at the same time. As DeNise explains, “As new breeds are developed, they may not appear as uniform as older breeds. When older breeds are crossed to create a new breed, there is some period of time before the new breed develops a unique DNA pattern of its own. In these cases, the more ancient breed sometimes appears in the new breed. The number of generations required to have a uniquely identified breed created from crossing of older breeds depends on the number of breeding animals in the new line, the severity with which the breed owners apply the standard, and the amount of introgressing [inbreeding, or breeding immediate relatives; line breeding, breeding close relatives; and backcrossing, breeding sibling to parent] allowed by the registration agency.”

Most people assume all mixed-breed dogs had a purebred ancestor at some time in their recent heritage. But in fact, this is not necessarily the case. When you run a mongrel’s DNA through a computer program, the algorithms attempt to group breeds together on a scatter chart. If the heritage of the dog is such that it is not in MMI’s database of 108 breeds, the program tries to find varieties that are most alike. Because at least one or two of the handful of ancient breeds are in every modern dog, sometimes the program will identify an ancient breed in the mix. “In the report we send to the client, we use the terms ‘primary,’ meaning the majority of the DNA matches a breed; ‘secondary,’ meaning less than the majority of the DNA but a strong influence nonetheless; and ‘in the mix,’ meaning the least amount of influence,” DeNise notes. That’s how you might get an obscure breed in the report. For instance, a 35-pound mongrel with a tablespoon of Husky and a teaspoon of Border Collie may also have a dash of Borzoi, because before gene pools were closed a century ago, Huskies were crossed with coursing hounds to add speed.

Don’t Judge a Pup by Her Cover
As MMI Genomics states on their certificates, “Your dog’s visual appearance may vary from the listed breed(s) due to the inherent randomness of phenotypic expression in every individual.” What this means is that you may look nothing like your parents, but you have Grandma’s great legs and Great Uncle Harry’s turned-up nose. All in all, though, no matter how genes are mixed and matched, your family members resemble one another. However, if Grandma was an Afghan Hound and Great Uncle Harry was a Pug, “random phenotypic expression” can be pretty extreme.

Researchers are intrigued by data that suggest expressed traits are somehow turned “on” and “off” by other genetic components, thus causing the wide variations in canine form and behavior. For instance, it’s possible that many breeds have the genetic potential for a black tongue, but only a few breeds have the molecular mechanism to switch that color on. So that black-tongued mutt may not have any Chow in the mix after all.

On the other hand, the results may show that a quintessential Heinz 57 has the genetic makeup of a single breed and it could be one she looks nothing like.

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