Scientists have completed a detailed DNA comparison of purebred pooches and found that a few hundred years of selective siring has resulted in significant genetic differences among breeds.

Elaine Ostrander of the Fred Hutchinson Cancer Research Center and the University of Washington and her colleagues collected tissue samples from 414 pedigreed dogs representing 85 breeds. By analyzing so-called microsatellites--short sequences of DNA that serve as signposts for genes--the team compared similarities and differences among the various kinds of dogs. According to the report, the microsatelite sequences from dogs of the same breed were much more similar to one another than they were to sequences from dogs belonging to different breeds. "These differences are so distinct that we could just feed a dogs genetic pattern into the database, and the computer could match it to a breed," notes study co-author Leonid Kruglyak, also at the Fred Hutchinson Cancer Research Center.

The findings, published today in the journal Science, could prove useful in the fight against a variety of human diseases. "There are more than 400 breeds of dog, and each is an isolated breeding population," Ostrander explains. "What that means is that each dog breed is like a little Iceland--an isolated population that allows us to simplify a complicated genetic problem." Because dogs suffer from many of the same afflictions that can strike people--cancer, heart disease and diabetes, among them--the authors hope that Fidos genome will help narrow the search for disease-causing genes in his owner.