A team of scientists from the United States, France, and the United Kingdom announced Thursday the first high-quality sequence of the domestic dog’s genome, a development that could help researchers sniff out the cause of many human ailments.

The summary explanation of the dog’s genetic code was published in Thursday’sissue of the journal Nature.

NatureThe 99 percent-complete sequence of a female boxer named Tasha adds to a partial survey of the poodle genome. By sampling the genomes of 10 different dog breeds the scientists have also managed to catalog about 2.5 million specific genetic differences across pedigrees.

These differences can serve as recognizable signposts for scientists to locate genetic contributions to the characteristics of different breeds well beyond their susceptibility to diseases.

"The incredible physical and behavioral diversity of dogs―from Chihuahuas to Great Danes―is encoded in their genomes,” said Eric Lander, director of the Broad Institute, professor of biology at MIT and systems biology at HarvardMedicalSchool.

“Man’s best friend, Canis familiaris, occupies a special niche in genomics,” said the paper. “With the exception of the human, dog is the most intensely studied animal in medical practice, with detailed family history and pathology data often available.”

Canis familiaris

The domestic dog’s lineage meets that of the grey wolf between 15,000 and 100,000 years ago. Originally domesticated in East Asia, dogs have evolved by sharing living space and food with humans, and in recent centuries through selective breeding.

These tightly controlled breeding programs (and occasional population bottlenecks during World Wars) have produced about 400 distinct modern breeds, often with high prevalence of specific diseases also seen in humans. These include cancers, blindness, heart disease, cataracts, epilepsy, hip dysplasia, and deafness.

“[This] suggests that a limited number of loci [genes] underlie each disease, making their genetic dissection potentially more tractable in dogs than in humans,” the paper said.

“If so, it is a significant step forward in understanding the roots of genetic disease in both dogs and humans,” said Kerstin Lindblad-Toh, co-director of the genome sequencing and analysis program at The Broad Institute of Harvard and MIT in Boston.

A Lead on Bone Cancer?

Dr. Lindblad-Toh’s team is studying a common type of childhood bone cancer in humans called osteosarcoma that also occurs frequently in Greyhounds and Rottweilers.

“The breeding history of the domestic dog created a unique genome structure that makes disease mapping much more powerful than in humans,” Elinor K. Karlsson, graduate student with Dr. Lindblad-Toh, told RedHerring.com in an email.

Working with humans, the team would have needed to examine at least 300,000 genomic markers in each of thousands of sick and healthy volunteers to even attempt to find the genetic trigger for this cancer.

“For our osteosarcoma study in dogs, we need 30 times fewer genomic markers and just a few hundred volunteers,” added Ms. Karlsson. “Anyone who owns a purebred dog, especially an older dog or a dog who has had cancer, can help with our research by sending us a blood sample from their dog.”

Genetic Insight into Mammals

The genomes of four mammals have so far been intensely analyzed: that of the human, chimpanzee, mouse, and rat. These all come from one of the four arms (known as clades) of placental mammals.

The dog, however, comes from another clade, which means that scientists can use it to more accurately triangulate which genes have been conserved through the evolutionary history of mammals.

Theory suggests that the more closely natural selection guards particular genes through time, the more important their function. As such, the new research could help identify particularly important genes in placental mammals.