An international team has tracked a million DNA variations in volunteers around the world, as part of an effort to map the diversity of human genes. Experts say the growing catalog, called the HapMap, will help to pinpoint genetic causes of disease and develop more effective treatments.

Researchers hope that by cataloging SNPs and the frequency with which they occur in different populations, they will boost efforts to target drugs at different genetic types. Because there are so many SNPs, the HapMap project aims to sort them in ways that will make such analyses easier.