POLYMORPHIC ADMIXTURE TYPING IN HUMAN ETHNIC POPULATIONS

A panel of 257 RFLP loci was selected on the basis of high heterozygos ity in Caucasian DNA surveys and equivalent spacing throughout the hum an genome. Probes from each locus were used in a Southern blot survey of allele frequency distribution for four human ethnic groups: Caucasi an, African American, Asian (Chinese), and American Indian (Cheyenne). Nearly all RFLP loci were polymorphic in each group, albeit with a br oad range of differing allele frequencies (delta). The distribution of frequency differences (delta values) was used for three purposes: (1) to provide estimates for genetic distance (differentiation) among the se ethnic groups, (2) to revisit with a large data set the proportion of human genetic variation attributable to differentiation within ethn ic groups, and (3) to identify loci with high delta values between rec ently admired populations of use in mapping by admixture linkage diseq uilibrium (MALD). Although most markers display significant allele fre quency differences between ethnic groups, the overall genetic distance s between ethnic groups were small(.066-.098), and <10% of the measure d overall molecular genetic diversity in these human samples can be at tributed to ''racial'' differentiation. The median 6 values for pairwi se comparisons between groups fell between .15 and .20, permitting ide ntification of highly informative RFLP loci for MALD disease associati on studies.