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Mapping the Bovine Genome To Help Cattle and Humans

In the near future, scientists may be able to improve production traits in cattle--and possibly help provide solutions to certain human health problems--thanks to the mapping of the bovine genome by scientists with the Agricultural Research Service and their colleagues around the world.

The project began in spring 2000 when Steven M. Kappes, director of ARS' Roman L. Hruska U.S. Meat Animal Research Center in Clay Center, Neb., began contacting labs around the world to develop a Bacterial Artificial Chromosome (BAC) map. Bacteria--and more specifically, bacterial chromosomes--are used as hosts for pieces of bovine chromosomes. The bacterial hosts are used to generate many identical copies of a piece, or clone, of cattle DNA. The BAC map will help scientists identify genes that affect production traits in farm animals and will help them sequence the bovine genome.

The first step is fingerprinting each of 280,000 BAC clones. This is done by cutting DNA from a BAC clone into pieces and separating the fragments on a gel. Researchers use the fingerprint pattern of the different fragments to identify overlapping BAC clones. A BAC map is the collection of overlapping clones that represent the entire bovine genome.

The second step, which can occur simultaneously with the fingerprinting, is sequencing both ends of all 280,000 clones. The scientists will combine the end sequencing and fingerprinting information to determine the overlapping BAC clones.

So far, 249,000 of the 280,000 cattle BAC clones have been fingerprinted, and the end- sequencing effort is under way. The completion date for the bovine BAC map is February 2003.

Once the project is complete, scientists may be able to more accurately select genetically superior animals for specific purposes, such as lean beef, milk production or reduced feed requirements. This research may also help the medical community, since cattle and humans have many of the same genes. Scientists will be able to compare the genetic maps of each species to possibly find cures for diseases.

ARS is the U.S. Department of Agriculture's chief scientific research agency.