The Polymerase Chain Reaction (PCR) involves three basic steps; denaturation, annealing and extension. In the denaturation step, DNA is heated at high temperature (94°C to 96°C) to separate the two strands. In the next step (annealing) the two oligonucleotide primers anneal to each single-stranded template DNA. This step is carried out at a lower temperature (40°C to 60°C). The final step is an extension, wherein Taq DNA polymerase synthesizes the DNA region between the primers, using dNTPs (deoxynucleoside triphosphates) and Mg²⁺ ions.