Dog DNA reveals man's link with best friend

by Medindia Content Team on  September 29, 2003 at 12:31 PM Drug News   - G J E 4
Dog DNA reveals man's link with best friend
Since the start in recent years of intense genetic sequencing, more than 150 species, mostly bacteria, have been completed, but the study appearing this week in the journal Science is the first for a companion animal.

A standard size poodle named Shadow, the family pet of gene researcher J. Craig Venter, provided the specimen that researchers used to sequence the canine genes.

"Shadow is now one of history's most valuable dogs," said Venter, founder and leader of one of the two teams that first sequenced the human genome.

The rough draft shows dogs have about 2.4 billion base pairs of DNA, or about half a billion fewer than humans. Genomic Researchers of the study say that genetic sequence is important for medical research because dogs share about 360 of the same genetic disorders that are known in humans. Dogs, they said, are second only to humans in the thoroughness of medical understanding and research.

All mammals, at one point, had a common ancestor. But dogs are known to have diverged toward an independent species about 95 million years ago. The mouse and humans both diverged about 87 million years ago, making mice closer to humans in time.

"We are much closer to the dog than to the mouse in terms of our gene content and structure," said researchers. "But if you do the evolutionary tree, we are on the same linage as the mouse. The mouse is evolving at a much faster rate." Researchers achieved what is called 1.5 X coverage of the dog genome.

This means many DNA fragments remain and the results are less accurate than the completed sequences of some other species. For instance, the mouse has been sequenced to a 8 X coverage, which is considered ideal and essentially complete.

But they said because of the genetic sequences already completed for other species, particularly the human and the mouse, their team was able through comparison to quickly identify genes and gene regulatory elements in the dog genome that match those in other mammals.

Using this technique from species to species will enable researchers to more quickly and at less cost identify the genetic source of many human disorders, they said. Researchers said their labs can now do three other mammal species, probably the whale, elephant and dolphin, for what it would have cost to carry the dog genome to an 8 X fidelity.

"We can do more species at lower cost and still annotate [identify] elements of the human genome with equal power," they said.

A more complete genetic sequencing of the dog is expected to be finished next year.


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