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By Sean Henahan, Access Excellence

DENVER A new gene mapping technique should greatly speed the work of geneticists involved in the international Human Genome Project, report researchers.

Researchers at the University of Colorado Health Sciences Center have developed a method called "STS gene mapping". The method developed by Dr. James Sikela, PhD, and his team uses a mapping marker (a genetic "bar code" ) called an STS, which can be used to determine the chromosomal location of any segment of DNA. STS stands for 'sequence tagged sites'.

In 1991, Sikela and associates showed how STSs could be rapidly generated from human genes so that each gene would have its own unique STS. Each STS could then be easily assigned to a chromosome, thus simultaneously mapping the corresponding gene. The team has now refined the technique, using new tools that have recently become available, so that a gene's exact location on a chromosome can be determined.

Locating genes associated with specific diseases has traditionally been a slow and painstaking process. The first step is usually to determine the approximate location of a disease gene on one of the 23 chromosomes. However, each section of a chromosome may have several hundred genes on it, so each gene must be located and tested individually to determine which one triggers a disease. This approach can take several years to complete. In the case of Huntington's disease, for example, it took researchers 10 years to identify the gene after the first marker was discovered.

Only about 5 percent of the estimated 50,000 to 100,000 human genes have been mapped so far. The new technique is already being used by an international consortium of scientists to develop the world's first detailed map of human genes. With the gene map, researchers will be able to quickly find the genes in virtually any region of any chromosome. Using the new method, researchers hope to produce a comprehensive gene map, showing the location of the majority of human genes by 1997.

"A comprehensive gene map will permanently change the way the majority of disease genes are discovered," said Dr. Sikela, associate professor of pharmacology. "Instead of spending many months and often years trying to find all the genes in a chromosomal region thought to contain a disease gene, a computer search of the gene map will get the same information in a matter of seconds."

For more details on the new technique, see Dr. Sikela's article in the August 1995 issue of Nature Genetics.

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