PCR (Polymerase Chain Reaction): It is the revolutionary method developed by Kary Mullis in the 1980s. PCR is based on using the ability of DNA polymerase to synthesise new strand of DNA complementary to the offered template strand. Because DNA polymerase can add a nucleotide only onto a pre-existing 3'-OH group, it needs a primer to which it can add the first nucleotide.
Primer used for the process of polymerase chain reaction are:

Explanation

Single stranded DNA oligonucleotide