The Phase II HapMap was produced using the same DNA samples used in the Phase I HapMap. That DNA came from blood collected from 270 volunteers from four geographically diverse populations: Yoruba in Ibadan, Nigeria; Japanese in Tokyo; Han Chinese in Beijing; and Utah residents with ancestry from northern and western Europe. No medical or personal identifying information was obtained from the donors, but the samples were labeled by population group.
To provide information on less common variations and to enable researchers to conduct genome-wide association studies in additional populations, NHGRI plans to extend the HapMap even further. Among the populations donating additional DNA samples are: Luhya in Webuye, Kenya; Maasai in Kinyawa, Kenya; Tuscans in Italy; Gujarati Indian in Houston; Chinese in metropolitan Denver; people of Mexican ancestry in Los Angeles; and people of African ancestry in the southwestern United States.
In its overview paper in Nature, the consortium estimates that the Phase II HapMap captures 25 percent to 35 percent of common genetic variation in the populations surveyed. The consortium also confirmed that use of Phase II HapMap data has helped to improve the coverage of various commercial technologies currently being used to identify disease-related variants in genome-wide association studies. Researchers did note, however, that current technologies tend to provide better coverage in non-African populations than in African populations because of the greater degree of genetic variability in African populations.
The overview paper also reports that the Phase II HapMap has provided new insights into the structure of human genetic variation. One new finding was the surprising extent of recent common ancestry found in all of the population groups. Tak
|Contact: Geoff Spencer|
NIH/National Human Genome Research Institute