An Icelandic genetics company says it has detected a version of a gene that more than triples the risk of heart attacks in African-Americans, a finding that is likely to sharpen the debate about the merits of race-based medicine. The company, DeCode Genetics, first found the variant gene among Icelanders and then looked for it in three American populations, in Philadelphia, Cleveland and Atlanta. Among Americans of European ancestry, the variant is quite common, but it causes only a small increase in risk, about 16 percent. But among African-Americans, while the variant gene was found in only 6 percent of...