Polymerase Chain Reaction ( PCR ) in Chemical Biology

Abstract The polymerase chain reaction (PCR) is a temperature‐controlled technique for amplifying DNAin vitro. It requires a DNA template; two oligodeoxynucleotide primers, which define the DNA to be amplified; the four deoxynucleoside triphosphates; and a thermostable DNA polymerase. PCR is carried out in a thermocycler, in which the DNA is subjected to cycles of denaturation of the double‐stranded DNA template; annealing of the two primers, which are complementary to the two strands of the DNA template; and DNA polymerization (primer extension). Because the product of one cycle serves as the template for the next cycle, PCR leads to the exponential amplification of the initial DNA template, which produces more than a million copies of a homogenous PCR product in 20 cycles. PCR has become an indispensable technique in all life sciences and is used extensively for research and diagnostic purposes. PCR applications include cloning of genomic DNA, preparing DNA for sequencing, site‐directed mutagenesis and recombination, genetic fingerprinting for forensic purposes, detection and identification of infectious agents, prenatal diagnosis of genetic diseases, identification of allelic sequence variations, and gene‐expression analysis.