May 4, 2009

Scientists Sequence Cow Genome

Photo of cattle in a field

The domesticated cow has become the first livestock mammal to have its genetic blueprint sequenced and analyzed. This major milestone in animal genetics provides new information not only about cattle biology but also about mammalian evolution.

Cattle have provided sustenance to humans with their hides, meat, milk and strength for 10,000 years. Researchers have now sequenced and analyzed the entire genome — the complete set of DNA — of the Hereford breed, which is used in beef production. The effort to sequence and analyze the bovine genome took 6 years and involved more than 300 scientists from 25 countries. It was funded primarily by NIH's National Human Genome Research Institute (NHGRI) and the U.S. Department of Agriculture (USDA).

The primary results appeared in 2 papers published on April 24, 2009, in the journal Science. More than 20 companion reports with more detailed analyses also appeared in journals from the open access publisher BioMed Central.

In the first Science paper, a team led by researchers at the Baylor College of Medicine, USDA's Agricultural Research Service (ARS), Georgetown University and CSIRO Australia estimated that the genome of the domestic cattle contains approximately 22,000 genes and shares about 80% of its genes with humans. The researchers also found that the organization of human chromosomes is closer to that of domestic cattle than to those of rats or mice.

In the second Science paper, a research team led by scientists at the Baylor College of Medicine, ARS and the University of Missouri compared 6 other breeds to the Hereford reference genome. They then performed follow-up studies on 497 cattle from 19 geographic and biologically distinct breeds.

The scientists unveiled a map charting key DNA differences, called haplotypes, among the branches of the bovine tree. This "HapMap" revealed that present-day cattle evolved from a diverse ancestral population from Africa, Asia and Europe. The Indian subcontinent, in particular, appears to be a major site of cattle domestication. Due to domestication, cattle have recently undergone a rapid decrease in genetic diversity.

The HapMap can now be used to track DNA differences between cattle breeds to help improve the quality and safety of beef and dairy products. "The bovine HapMap will be a valuable resource and will transform how dairy and beef cattle are bred," says Dr. Richard Gibbs of the Baylor College of Medicine.

These findings will also help researchers understand the genetic basis for disease in cattle. That could lead to improvements in cattle health and potentially reduce producers' dependence on antibiotics. The results might also be used to reduce the environmental impact of cattle, such as the greenhouse gases released by herds.

In addition, the cattle genome will likely give us insight into our own genome. "By comparing the human genome to the genomes of many different species, such as the domestic cattle, we can gain a clearer view of how the human genome works in health and in disease," says acting NIH Director Dr. Raynard S. Kington.

Related Links