The idea of admixture mapping is to screen through the genome of populations of mixed ancestry such as African American, searching for regions where the proportion of DNA inherited from either the ancestral European or African population is unusual compared with the genome wide average. Admixture mapping requires a relatively small number of markers for a whole genome scan: a couple of thousand, rather than the hundreds of thousands estimated to be necessary in nonadmixed populations. Because the mixture between European and West-African populations occured within the past 15 generations, stretches of DNA with contiguous European and African ancestry have not had much time to break up because of recombination and typically extend millions of base pairs. Admixture mapping therefore studies highly selected SNPs every few million base pairs, rather than every few thousand as with linkage disequilibrium mapping.
and one of the main conclusions from this study:
...we show that the 8q24 locus contributes to a major increased risk for prostate cancer in African Americans with African ancestry at 8q24. The difference between these individuals and African Americans with European ancestry at 8q24 explains a large proportion of prostate cancer in younger African Americans.
Admixture mapping identifies 8q24 as a prostate cancer risk locus in African American men
Matthew L. Freedman,
PNAS: Early Edition