The researchers found that the DNA sequences of microsatellites from dogs within a breed were much more similar than those among breeds. Microsatellite "signatures" for each breed were distinct enough that they could be used to categorize 99 percent of the individual dogs into their correct breeds.

"The fact that we were able to do this with so few dogs from each breed tells us that the microsatellites-and therefore, probably many of their genes-are very common among members of a breed," Parker said. That finding also means that the approach could be used to verify that a dog truly belongs to a particular breed if its ancestry is in question.

Based on the genotyping analysis, the researchers were able to sort the breeds into four groups of genetically similar varieties, which presumably share common ancestry. Some of the relationships between breeds had not previously been known.

One of the four clusters represents an ancient group of animals with Asian and African origins that possess a wide diversity of traits. This group includes breeds such as the Alaskan Malamute and Siberian Husky and shows the closest relationship to the wolf, the direct ancestor of the domestic dog.

"This group may be telling us something about the original domesticated dog population," Kruglyak said.

One of the other three other groups contains Mastiff-like breeds that share common physical characteristics. Another includes Shetland and Belgian sheepdogs, Collies and other dogs with herding behaviors. The fourth group includes animals with hunting-associated behaviors.

Parker said that research groups, including Ostrander's lab, are using information from their analysis to study specific canine diseases.

"We're now looking at narrowing down similar regions of DNA to identify single genes that contribute to particular traits," she said. "There are hundreds of diseases out there, and many of them have counterparts in humans."

In addition to cancer, the Ostrander lab is studying genetics of blindness and soon will begin a study on genetics of obsessive-compulsive disease. "What is so great about this study to date is that it's been a real community effort," Ostrander said. "We could not have done the work without the involvement of pet owners, breeders and community leaders who support the work we're doing to improve both canine and human health. This is just the way science is supposed to be done." fhcrc