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. The UNG treatment is performed at 50°C for 2 min at the onset of the cycling program. Uracil-N-glycosylase is inactivated by incubation at 95°C for 10 min.