"For genes this is not unexpected, since most mammals share a rather similar set of genes," said Hans Ellegren, an evolutionary biologist at Uppsala University in Sweden.
"However this indicates that there is a core set of noncoding sequences needed to make a mammal."
The researchers have also found that many of the conserved sequences are clustered around developmental genes.
"You could imagine these could be genes [that are] really important for body planning and development," Lindblad-Toh said.
Dogs were the first animals to be domesticated some 15,000 years ago. They all originate from a single species, the wolf, but modern breeds display a wide diversity of traits.
To understand the genetic basis for this diversity, the researchers compared DNA samples from another ten dog breeds.
They also compiled a catalogue of 2.5 million genetic units that vary between different dogs. The units will help researchers identify nearby genes that are responsible for traits such as disease susceptibility.
"The fact that only a few breeds typically show a disease means that by searching for genetic dissimilarities between breeds, there is a decent chance of finding genes that cause the [disease] between breeds," said Ellegren, the Uppsala University biologist.
Dogs suffer from more than 350 genetic disorders, many of which resemble human conditions. The most common diseases among purebred dogs include cancer, epilepsy, heart disease, allergies, retinal disease, and cataracts.
"[This research] increases the possibility of using dogs as a model for human disease," Ellegren said.
The study could also help researchers identify genes that govern behavioral traits, such as aggressiveness or kindness.
In addition, the data suggests how dogs were domesticated. The amount of genetic diversity across breeds is consistent with a "bottleneck"a strong reduction in genetic varietythat occurred between 10,000 and 15,000 years ago.
"This bottleneck is likely to have been [due to] domestication," Ellegren said.
Within breeds there are also signs of strong bottlenecks just 50 to 200 years ago, suggesting most dog breeds have a very recent origin.
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