ABSTRACT
Polymerase chain reaction (PCR) is an extremely simple yet immensely powerful technique. It allows enormous amplification of any specific sequence of deoxyribonucleic acid (DNA) provided that short sequences either side of it are known. PCR consists of three steps: Denaturation; Primer annealing; and Elongation. PCR can amplify a single DNA molecule from a complex mixture, largely avoiding the need to use DNA cloning to prepare that molecule. Variants of the technique can similarly amplify a specific single ribonucleic acid (RNA) molecule from a complex mixture. DNA sequencing has been greatly simplified using PCR, and this application is now common. PCR is exquisitely sensitive and can amplify vanishingly small amounts of DNA. PCR is now invaluable for characterizing medically important DNA samples.
