A new technique, admixture mapping, takes advantage of the higher-risk genetic segments from one population that show up in the other through generations of racial mixing. The presence of higher-risk segments in the otherwise lower-risk DNA makes for more efficient sorting of the genome to zero in on disease genes. The study, led by David Reich, linked MS for the first time with a region on chromosome 1. Since no gene has yet been pinpointed, the researchers are treating their results as promising evidence that the method may be a valuable additional tool to identify new pathways important in disease.