Uracil-N-glycosylase is a pure recombinant enzyme expressed in E. coli. UNG is used in PCR and real-time PCR to prevent carryover contamination between reactions. The enzyme removes uracil from any dU-containing contaminating amplicons, leaving abasic sites and making DNA molecules susceptible to hydrolysis during the initial denaturation step. To enable PCR amplicons to be degraded, dTTP must be partially or completely substituted by dUTP. Uracil-N-glycosylase is inactivated by incubation at 50°C for 5 min.