Polymerase Chain Reaction (PCR) is an in vitro technique for the amplification of a specific DNA region without prior transfer into living cells. It is a powerful technique because a million-fold amplification can be achieved only in a few hours. For the carrying out of PCR, pair of primers are needed that flank the DNA region to be amplified. A primer is an oligonucleotide with a nucleotide sequence complementary to the nucleotide sequence in
the DNA template. This paper will discuss the general principles of PCR, the detailed procedure for carrying out the PCR and the various factors affecting the optimal PCR results. This technique was introduced by Kary Mullis in 1985, for which he obtained the Nobel Prize in 1993.