The Polymerase Chain Reaction (PCR) is a technique widely used in molecular biology in order to amplify small segments of DNA (100 to 1000 bases). PCR uses a thermostable DNA Taq polymerase that adds nucleotides to the DNA template at the position specified by short single-stranded DNA primers that bind to this template by complementary base pairing during the annealing phase of the PCR cycle. Subsequently, the DNA polymerase adds deoxynucleotide triphosphates (dNTPs) to the opposite DNA strand, this phase of the PCR cycle is known as the elongation phase. Finally, the resulting double-stranded DNA fragment is separated by heat during the denaturation step and this 3-step PCR cycle is repeated many times to amplify the target DNA region.
