A Good SNP May Be Hard to Find

HUMAN GENOMEAcademic and corporate labs alike are mining the human genome for minute differences between individuals called single-nucleotide polymorphisms (SNPs). Many researchers hope that random collections of these mutations will yield a shortcut to identifying the genes underlying such major diseases as asthma or cancer. New findings suggest, however, that the payoff may be slow, because the SNPs that directly influence disease risk are scarce.