The polymerase chain reaction (PCR) and RT-PCR

Abstract

The polymerase chain reaction (PCR), a method for the in vitro enzymatic amplification of DNA, has facilitated greatly the analysis of complex genomes by permitting the characterization and cloning of DNA sequences from small samples of DNA or RNA of high sequence complexity. PCR and its specialized variants are now used as widely as any of the ‘older’ methods in molecular biology of nucleic acids, for several reasons. First, through amplification of specific DNA sequences, or RNA sequences following reverse transcription, PCR can replace the construction of genomic or cDNA libraries for cloning. Second, PCR can simplify most analytical and synthetic procedures that follow gene cloning, such as subcloning, sequencing, synthesis of probes, mutagenesis and construction of gene fusions (Clackson et al., 1991). Finally, the ability to amplify DNA from extremely small samples by PCR has revolutionized molecular genetic analysis (Erlich and Arnheim, 1992).