Could lead to better breeding techniques, shed light on human genome
THURSDAY, April 23 (HealthDay News) -- A consortium of more than 300 researchers in 25 countries has succeeded in sequencing the entire genome of the placid, farm-dwelling cow.
The feat has implications for understanding the biology of this bovine and related creatures (even humans), and sheds light on some evolutionary history, said the authors of two reports in the April 24 issue of Science.
Most importantly, the mapping of the cow genome could portend ways to improve and increase the world's food supply.
Whereas, in the past, the "genetic merit" of the milk-production capability of a bull's female offspring took five years to assess, things will now move much more quickly, said Jeremy Taylor, co-author of one of the reports and Wurdack Chair in Animal Genomics at the University of Missouri. "The bull is born, we can pull a few hairs out of his tail and predict his genetic merit for the milk-producing capability of his daughters with an accuracy of 70 percent."
Seventeen countries, including the United States, have already adopted this technology, Taylor added.
"We can choose the cattle not only based on their traits but also based on the sequences of the genes that matter," said Bret Payseur, an assistant professor of medical genetics at the University of Wisconsin, Madison. "You can imagine that that's going to be much more efficient."
"This will make the identification of genes that are important in traits having to do with food production, milk quality and meat quality easier to identify. In breeding, it's going to help with tracking those traits and perhaps making selective breeding a faster process because we may be able to identify the genes that are involved [earlier]," added Kim C. Worley, co-author of one of the reports and an associate professor in the Human Genome Sequencing Center at Baylor College of Medicine in Houston.
The information yielded from sequencing may one day even lead to a "safer" cow by identifying breeds that are more susceptible to maladies such as "Mad Cow" disease (bovine spongiform encephalopathy), she added.
This is the first livestock genome to be published.
The two papers cover findings from two projects: the Bovine Genome Sequencing and Analysis Consortium, which mapped the genome, and the Bovine HapMap Consortium, which looked at genetic diversity among cattle.
The genome of the cow has at least 22,000 genes, which is almost identical to the number found in humans. Most of the genes are also identical so, for instance, both cows and humans have a gene for growth hormone, Taylor said.
Scientists were able to tell that cows have specialized genes that help them metabolize food. And both genomes may have adapted to each other.
"Humans drink a lot of cow's milk and that's resulted in a change in the human genome so we are lactose-tolerant," Taylor said.
In fact, the cow gene sequence and the chromosomal arrangements are more similar to humans than rodents. "That means when we try to understand human biology by studying genes in related organisms, we may be better off looking at the cow sequence for a lot of functions we study in mice and rats," Worley said.
Will cows replace white mice as in the lab? Probably not, but they may become more important in fields such as neurology, where humans and rodent systems diverge considerably, as well as metabolic diseases.
The papers also amassed a tremendous amount of historical information about the now-placid bovines.
"We were able to construct a tree of life that showed there were two focused areas [the Indian Subcontinent and the Fertile Crescent] about 10,000 to 11,000 years ago where humans figured out how to domesticate these animals," Taylor said. "These would have been about 2,000 pounds of meanness, and little human beings of about 100 pounds were able to capture and breed them and tame them."
And there is knowledge even beyond that.
"If you compare the human genome to that of rodents, dogs and now cattle, we can see that there are 1,000 genes that are shared between rodents, dogs and cattle but missing from the human genome," Payseur said. "Those could be mistakes in the human genome sequence but a more interesting possibility is that those genes are telling us something about what it means to be human."
Visit the U.S. National Human Genome Research Institute for more on genomic sequencing.
SOURCES: Kim C. Worley, Ph.D., associate professor, Human Genome Sequencing Center, department of molecular and human genetics, Baylor College of Medicine, Houston; Bret Payseur, Ph.D., assistant professor, medical genetics, University of Wisconsin, Madison; Jeremy Taylor, Ph.D., Wurdack Chair in Animal Genomics, University of Missouri, Columbia; April 24, 2009, Science
All rights reserved