Friday, September 15, 2006

Gene Chips for Cows

Applying cutting-edge genomics techniques to cattle might produce more milk and tastier beef.

By Emily Singer

Steak fans may soon reap the benefits of the genomics revolution. A new project will help scientists create bovine breeds genetically selected to produce bountiful supplies of perfectly marbled steaks.

Scientists at several U.S. and Canadian research institutes are collaborating with Illumina, based in San Diego, CA, to develop a bovine gene chip, similar to those used to study the genetics of human disease. The DNA chips, expected to be on the market early next year, will dramatically speed the search for the genetic variants that underlie desired traits, such as the level of marbling in a cut of meat or the efficiency of a dairy cow's milk production.

"This opens a whole new scale of gene identification in cattle," says Jerry Taylor, professor of animal genomics at the University of Missouri-Columbia and one of the researchers on the project. "We'll be able to tackle genetics of all of these traits--reproductive capability, milk production, milk composition, and quality of meat--in ways we never before envisioned."

The sequence of the cow genome was released last year, but scientists have made little progress in identifying genes associated with desirable bovine traits, for the same reasons that have slowed human studies of complex genetic diseases: vast amounts of genetic data are needed to narrow down the gene variants linked to a particular trait.

Now scientists are planning to pool data from revised drafts of the bovine genome and other studies to create this genetic tool--a tiny glass chip coated with thousands of short sequences of DNA that can detect sites in the genome that frequently differ among individuals. Researchers at the U.S. Department of Agriculture, University of Missouri-Columbia, and University of Alberta are now choosing the specific sequences that will be included on the chip.

The chips will allow scientists to quickly and cheaply gather genetic data on huge numbers of cattle. Scientists can take a DNA sample from an animal and use the chip to simultaneously detect thousands of genetic variations, giving a detailed profile of that animal's genome. Thousands of individual profiles are then analyzed in conjunction with data on each animal's phenotype (its observable, physical characteristics) to determine the variations associated with a particular characteristic, such as growth rate.