[troutman]

How does this work? Aren't most domestic breeds recently developed by artificial selection? What markers would these new breeds have to distinguish them?

http://news.vin.com/VINNews.aspx?articleId=23206

Five years since companies introduced commercial dog breed identification genetic tests, veterinarians continue to wonder if the tests are valid. Hoping to find the answer, the VIN News Service put the tests to the test.

We submitted DNA samples on six dogs to compare the results and check for consistency. We knew the breed backgrounds of four of the dogs, so were able to determine whether the tests gave correct answers.

The concept of determining a dog’s breed background by analyzing its DNA is grounded in science. In a paper published in the journal Science in 2004, canine geneticist Elaine Ostrander and colleagues described a technique they developed for identifying dog breeds based on genetic markers. Ostrander, who currently works at the National Human Genome Research Institute, part of the National Institutes of Health, described the approach, along with her broader work on the canine genome, in an article published in 2007 by American Scientist.

The markers the researchers used are not genes themselves, but repeating sequences of DNA known as microsatellites. The commercial tests use a different kind of marker known as single-nucleotide polymorphisms — abbreviated SNPs and pronounced like "snips” — that are small mutations within the genome. Whether using microsatellites or SNPs, the markers, taken together, form signatures particular to each breed.

Because the identification technique is not based on genes, it does not specifically relate to physical or behavioral traits that characterize particular breeds. In other words, the technique doesn’t recognize a bulldog by finding the genes that give it a snub nose, beefy head and squat stature.

Breeds have distinctive genetic signatures owing to the fact their members are genetic isolates — that is, bred from a limited population of dogs. The more unique the breed characteristics, the easier to identify a breed's members via their DNA. Explained Dr. Urs Giger, a veterinarian who heads the clinical program in medical genetics and pediatrics at the University of Pennsylvania (UPenn) School of Veterinary Medicine: “The more you’re inbreeding ... that will clearly make the genes among the dogs more similar.”

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