ABSTRACT
The polymerase chain reaction (PCR) allows an extremely large number of copies to be synthesized of any given DNA sequence provided that two oligonucleotide primers are available that hybridize to the flanking sequences on the complementary DNA strands. PCR consists of three steps: Denaturation, primer annealing and elongation. PCR has very widespread applications, and new uses are being devised on a regular basis. Some of the applications are as follows: 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 RNA molecule from a complex mixture. PCR is exquisitely sensitive and can amplify vanishingly small amounts of DNA. PCR is invaluable for characterizing medically important DNA samples. The PCR screen is based on the analysis of microsatellites.
