Appendix

The kinetic analysis of the gel fidelity assay for polymerases with exonucleolytic activity was derived assuming SCH1 (1). Occasionally, however, polymerase fidelity is too high or processivity is too low to detect misincorporation under standard SCH conditions (defined by Poisson statistics as <20% of p/t DNA extended). Greater quantities of p/t DNA can be exposed to SCH conditions by using trap DNA, which sequesters a polymerase after it dissociates from a p/t. Alternatively, the reaction can be run into MCH conditions.