Polymerase Chain Reaction?

-The polymerase chain reaction (PCR) is a biochemistry and molecular biology technique for isolating and exponentially amplifying a fragment or sequence of interest of DNA, via enzymatic replication, without using a living organism (such as E. coli or yeast).
-As PCR is an in vitro technique, it can be performed without restrictions on the form of DNA, and it can be extensively modified to perform a wide array of genetic manipulations.

PCR principle and procedure

-PCR is used to amplify specific regions of a DNA strand.
-This can be a single gene, just a part of a gene, or a non-coding sequence.
-PCR, as currently practiced, requires several basic components
These components are:
1) DNA template that contains the region of the DNA fragment to be amplified
One or more primers, which are complementary to the DNA regions at the 5' and 3' ends of the DNA region that is to be amplified.

2) A DNA polymerase (e.g. Taq polymerase or another DNA polymerase with a temperature optimum at around 70°C), used to synthesize a DNA copy of the region to be amplified

3) Deoxynucleotide triphosphates, (dNTPs) from which the DNA polymerase builds the new DNA

4) Buffer solution, which provides a suitable chemical environment for optimum activity and stability of the DNA polymerase

5) Divalent cations, magnesium or manganese ions; generally Mg2+ is used, but Mn2+ can be utilized for PCR-mediated DNA mutagenesis, as higher Mn2+ concentration increases the error rate during DNA synthesis

6) Monovalent cation potassium ions

The PCR is carried out in small reaction tubes (0.2-0.5 ml volumes), containing a reaction volume typically of 15-100 μl, that are inserted into a thermal cycler. This machine heats and cools the reaction tubes within it to the precise temperature required for each step of the reaction.


Credits: http://en.wikipedia.org/wiki/Polymerase_chain_reaction