May 20, 2004 -- The same genetic traits that make a border collie a born herder or a beagle sniff out its prey may offer new clues into the human disease process, according to a new study.
The study showed that each of the 85 varieties of purebreds analyzed has its own genetic signature or DNA blueprint, which is responsible for the breed's unique traits. But researchers found that differences among the breeds accounted for only 30% of the genetic variations seen.
They say that purebreds share many genetic similarities with other breeds. Researchers say understanding those genetic relationship between breeds should allow them to discover the genes responsible for not only the physical and behavioral traits of the breed but also the genes linked to the diseases to which the breeds are susceptible, such as cancer, deafness, blindness, and hip problems.
"Although there may be just as many genes for a given disease in dogs as there are in humans, being able to search for them in a single breed allows us to find the one or two genes responsible for that disease in that population much more easily," says researcher Elaine Ostrander, a geneticist at the Fred Hutchinson Cancer Research Center in Seattle, in a news release.
"There are more than 400 breeds of dog, and each is an isolated breeding population," says Ostrander. "What that means is that each dog breed is a like a little Iceland -- an isolated population that allows us to simplify a complicated genetic problem."
Dog Genome Offers Clues for Humans
In the study, which appears in the May 21 issue of the journal Science, researchers used molecular markers to look at genetic relationships in 414 dogs from 85 domestic dog breeds.
The study revealed a set of molecular markers unique to each breed. The genetic molecular marker sequences from dogs within a certain breed were much more similar than those among different breeds.
Differences between the breeds, however, accounted for about 30% of the genetic variation.
Researchers say that level of diversity within the species is unprecedented.
"Most breeds have been artificially created by man," says researcher Heidi Parker, a graduate student at the cancer center, in the release. "Although all are members of the same species, this selective breeding has resulted in amazing variation between breeds with respect to weight, size, head shapes, coat, ear shape, behaviors, and diseases."
Based on the analysis, researchers were able to sort the breeds into four groups of genetically varieties that they believe share common ancestry. Some of these genetic connections had not been previously known.
For example, one of the clusters represents an ancient group of animals with Asian and African origins that have a wide variety of traits. The group includes the Alaskan malamute and Siberian husky and shows the closest relationship to the wolf, the direct ancestor of the domestic dog.
Other groups include:
- Mastiff-like breeds that share common physical characteristics
Shetland and Belgian sheepdogs, collies, and other dogs with herding behaviors
Animals with hunting-associated behaviors, such as beagles
Using this information, researchers plan to study specific canine diseases that tend to cluster within breeds. Researchers say that at least half of the 300 inherited canine disorders, including cancer, resemble similar diseases in humans, and this research should offer new information on the genetic cause of human diseases.