The International HapMap Project is analyzing DNA from populations with African, Asian, and European ancestry. Together, these DNA samples should enable HapMap researchers to identify most of the common haplotypes that exist in populations worldwide. [See What Is the HapMap?]
Because of the history of the human species, most of the common haplotypes in human chromosomes occur in all human populations. [See The Origin of Haplotypes.] However, any given haplotype may be more common in one population and less common in another, and newer haplotypes may be found in just a single population. Efficiently choosing the tag SNPs needed to identify haplotypes therefore requires looking at haplotype frequencies in multiple populations. Also, genetic data from more than one population will enhance the ability of researchers to study the genetic contributions to diseases that are more or less prevalent in different groups.
The DNA samples for the HapMap have come from a total of 270 people. The Yoruba people of Ibadan, Nigeria, provided 30 sets of samples from two parents and an adult child (each such set is called a trio). In Japan, 45 unrelated individuals from the Tokyo area provided samples. In China, 45 unrelated individuals from Beijing provided samples. Thirty U.S. trios provided samples, which were collected in 1980 from U.S. residents with northern and western European ancestry by the Centre d'Etude du Polymorphisme Humain (CEPH).
The blood samples are being converted into cell lines, which are used to make DNA, by the non-profit Coriell Institute for Medical Research. Coriell provides DNA and cell lines from the samples for research projects that have been approved by the appropriate ethics committees. The samples and cell lines are not linked to any individual in the populations studied. However, the samples and cell lines are identified as coming from one of the four populations participating in the study, which raises ethical issues associated with conducting genetic research in named populations. [See How Are Ethical Issues Being Addressed? and Guidelines for Referring to the HapMap Populations in Publications and Presentations.]
To assess how much additional information would be gained by genotyping other populations, haplotypes in a set of chromosomal regions are being analyzed in samples from several additional populations.