How to Understand It Components of the Pcr

COMPONENTS OF THE PCR The fi ve components of the basic PCR are: 1 A source of template DNA containing the target sequence to be amplifi ed (Fig. 1). This template can be either total genomic DNA containing exons* and introns*, or complex cDNA* mixtures. 2 Two short single-stranded sequences of DNA termed ‘primers’ or ‘amplimers’, designed on the basis of previous knowledge of the DNA target sequence. They fl ank the region of interest to be amplifi ed. The ‘upstream’ primer has a sequence complementary to the seThe polymerase chain reaction (PCR) is the single most important tool in biological sciences that has been developed in the last 20 years, with numerous applications in research and diagnosis. It is a test-tube method to selectively copy specifi c target DNA sequences – within a given source of DNA – and was ‘invented’ in 1986 following the identifi cation of a specifi c DNA polymerase* that can withstand repeated heating to high temperatures. It came into widespread laboratory practice when effi cient thermal cycling machines became available. *Terms used throughout this paper are defi ned in the Glossary.