(1) Denaturation: double-stranded DNA molecules are melted or denatured at high temperature (95°C) to give single-stranded targets for duplication. (2) Annealing: the temperature is lowered to a suitable annealing temperature (50°C). Short synthetic pieces of DNA or primers are bound to the single-stranded target sequences and prime DNA synthesis by Taq polymerase. (3) Extension: the temperature is raised to the optimal temperature for Taq polymerase (72°C). A cycle of amplification is completed and the process can be repeated, theoretically doubling the amount of product with each cycle in an exponential manner until a maximal level or plateau is achieved.