Its name was coined from one of its key processes i.e. DNA polymerase. A DNA template is produced and the chain reaction that follows is the concluding part of the process.
A major requirement of recombinant DNA techniques is the "availability of large quantities of specific DNA segment" (Bastianutto et al 2006). Cloning which was the preferred method involves transformation of a plasmid vector into bacteria that is then cultured. The cloning process is not as efficient as PCR in terms of amplification of DNA. In addition PCR can allow the generation of millions of copies of DNA from a single or few pieces.
PCR occurs in stages, the Initialization, Denaturation, Annealing, Extension/elongation, Final elongation. The Initialization step involves heating to 94-96'C. After the heating stage, Denaturation produces a single DNA strand. This is caused by breaking the hydrogen bonds between DNA strands, thus causing the melting of the DNA template and primers. Temperature is lowered during the annealing step. Here primers are bound to the single stranded DNA template by the polymerase. At the Extension/elongation the DNA polymerase produces a new DNA strand by adding dNTPs. The last PCR cycle is the Final elongation, the step is done to ensure that all single stranded DNA are fully extended.