Direct sequencing of long polymerase chain reaction fragments

Direct sequencing of polymerase chain reaction (PCR)-generated templates is a commonly used technique in molecular biology laboratories. We describe an improved method for direct sequencing of PCR fragments longer than 20 kb obtained with a commercial mixture ofTaq andPwo DNA polymerases. The sequencing protocol was optimized for an automated infrared DNA sequencer, consistently yielding long reads (500–600 bases).