Single nucleotide polymorphisms (SNPs) are useful physical markers for genetic studies as well as the cause of some genetic diseases. To develop more reliable SNP assays, we examined the underlying molecular mechanisms by which deoxyribonucleic acid (DNA) polymerases with 3′ exonuclease activity maintain the high fidelity of DNA replication. In addition to mismatch removal by proofreading, we have discovered a premature termination of polymerization mediated by a novel OFF-switch mechanism. Two SNP assays were developed, one based on proofread...
