In a PCR experiment approximately 1 unit of the Taq enzyme should be used for a 25μl reaction. Suboptimal concentration of the Taq enzyme can cause incomplete primer elongation or premature termination of the PCR product synthesis during the elongation step of a PCR cycle.

Too much Taq will result in an excessive background of unwanted DNA fragments (a smear on a gel) while a huge excess may cause the reaction to fail with no product being detected. A Taq concentration of 1 unit per 25μl reaction ensures a cleaner product and lower background.

Further reading:

1. PCR Books
2. Real-Time PCR: Current Technology and Applications
3. Real-Time PCR in Microbiology: From Diagnosis to Characterization
4. PCR Troubleshooting: The Essential Guide

Labels: PCR, PCR troubleshooting, real-time PCR, Taq