Low Percentage Traits in DNA

[linda holub 2]

After researching the breeds which showed up as low DNA percentages in my “purebred” dogs I realized that even at only 2 or 3 percent traits have shown up as dominant features in either their personality or body shape.

So my question is why doesn’t the percentage increase when the feature shows up in the animal? Is DNA somewhat static so that in itself it can’t predict personality or body shape?

(Examples – with only 3% Norfolk Terrier my Yorkie picked up this body shape and with only 3% my poodle looks more like a Havanese than a poodle. The physical bits are visual and obvious but I’m also seeing low percent personality traits show up as dominant traits in some of them. It seems there is a lot for geneticists to unravel)

[kathleen morrill]

Hi Linda,

Those 2-3% portions of your dog’s DNA might in a region of the DNA that influences those traits — body shape and personality — though there’s still much to discover.

Scientists use an approach called “ancestry mapping” to find those regions that influence traits based on ancestry. We will be using this approach to study behavior in a few ways; for example, studying retrieving behavior by looking at Poodles, Retrievers, and a variety of “-doodles”.

Say there is a part of the DNA that influences whether a dog fetches. A 4/5 Poodle & 1/5 Golden Retriever might be a fetching fanatic because they have retriever ancestry at that place in their DNA; likewise, a 1/5 Poodle, 4/5 Labrador might not be into fetching, just because they don’t have retriever DNA at that spot. This is what we hope to find out using ancestry mapping!

As for DNA being static — yes, and no. The genetic code of DNA is very stable, but many traits are not dominant-recessive and depend on many parts of DNA as well as environmental factors.

Kathleen

[Jennifer]

One thing I’ve noticed, in browsing a subreddit where people share their dogs’ DNA breed test results, is that people can sometimes be quite resistant to accepting a finding that their mutt contains only a very small percentage of “Breed X,” when said mutt happens to have inherited some particularly dramatically visible trait associated with “Breed X.” For example, a dog who has a merle coat pattern, or whose coat texture is wiry-scruffy with facial bearding. Both those traits are dominant or co-dominant and caused by just one gene, so even a tiny amount of ancestry from a merle or wiry-coated breed could be sufficient to cause them if the portion of DNA inherited from that ancestor happened to include that gene. But they’re also both very “loud” traits visually, and that loudness can trick us into assuming that there must be “a lot” of some merle or wiry-coated breed in there. And once you’ve gotten that idea into your head, it can be easy to then proceed to convince yourself that your mutt “clearly” also shows other, more vaguely defined and/or multi-gene traits associated with that breed, like “high energy” or “feisty” or “fast” or “leggy”–these are all pretty relative terms, and someone with years of experience in a breed commonly described as having them may understand them quite differently than the average person.

Also, even within most pure breeds, there’s sufficient diversity present in the collective gene pool to yield individuals who may be quite far off the norm or ideal for that breed (as epitomized by show or field champions) in both looks and behavior. Sometimes this gets read simply as that individual being a “faulty” example of the breed, other times it may lead to accusations or suspicions that the individual isn’t really purebred. There can be characteristic variations within lines, too; for example, German Shepherds bred for police work are as a group likely to display a somewhat different balance of behavioral and perhaps physical traits than those bred for seeing eye dog work, which in turn will look and act somewhat different than GSDs bred for show ring success. Backyard-bred and puppy mill dogs of a given breed, who generally haven’t been bred according to any selection criteria at all–just “whatever two dogs of this breed I happened to already own”–are especially likely to display variation from the breed standard, because standards are meant to define an ideal that breeders must keep continuously and rigorously selecting for; they aren’t meant to summarize all possible individuals that could result from the genetic diversity naturally present in the breed.

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