1. National Human Genome Research Institute, National Institutes of Health, Building 31, Room 4B09, 9000 Rockville Pike, Bethesda, MD 20892, USA.
2. The Wellcome Trust, 183 Easton Road, London NW1 2BE, England.
3. U.S. Department of Energy, 1000 Independence Avenue, S.W., Washington, DC 20585, USA.