Polymerase chain reaction (PCR)

The polymerase chain reaction (PCR) is a scientific technique in molecular biology to magnify and increase a single or a few copies of a piece of DNA across various extent, generating thousands to millions of copies of a particular DNA sequence (White, 1993). One of the major concept in PCR is thermal cycling, a process where the sample is heated and cooled alternately into a defined series of temperature steps.

During thermal cycling, two strands of the DNA double helix gets separated under high temperature. After heating, the sample is then cooled, where DNA polymerase uses each strand as a template to select the target DNA (Narayanasamy, 2010). The DNA polymerase used are also heat stable. An example will be Taq polymerase, an enzyme originally isolated from the bacterium Thermus aquaticus (Maier, 2009).

This DNA polymerase, through enzymatic action, assembles a new DNA strand from nucleotides (Mullis, 1994). This process is done by using single-stranded DNA as a template and DNA oligonucleotides, which are required for initiation of DNA synthesis (White, 1993). PCR is used in functional analysis of genes, the diagnosis of hereditary diseases and infectious diseases. PCR’s ability in targeting selected DNA also made this process widely used in genetic manipulation (Maier, 2009).

author: monica