The amplification of picogram quantities of DNA with the polymerase chain reaction (PCR) (1,2) targets specific nucleic acid sequences without the need for cloning, subcloning, and plasmid amplification (3). However, although the purity of amplified DNA products can be enhanced by strategies that avoid false priming events during amplification, such as reamplification with nested primers (4) or “hot start” PCR (3,5,6), ultimately it can only be achieved by the subsequent cloning of individual products.