The Polymerase Chain Reaction (PCR)

The polymerase chain reaction (PCR) is a processgenetic manipulations, diagnostic tests, and for
for amplifying very tiny amounts of DNA suchmany other uses. (Reference: Real-Time PCR:
that they can be visualized and assessed or usedCurrent Technology and Applications ISBN:
in further scientific processes. PCR is widely used978-1-904455-39-4)
in almost all branches of biology including molecularModern variations of PCR include Real-time PCR.
biology, microbiology, genetics, environmentalThis technology allows the newly generated DNA
science, food science, biotechnology, forensicmolecules to be analysed immediately they are
science, and clinical diagnostics. The PCR techniqueproduced. This ability to monitor the PCR process
involves using an enzyme called DNA polymerasein real time, while the reaction is still occuring, is of
to amplify (duplicate many times) a piece of DNA.enormous benefit to scientists as it reduces the
The original molecule of DNA is duplicated by theamount of time required to generate a result
DNA polymerase enzyme, thus doubling the(especially important in clinical diagnostics) and also
number of DNA molecules.enables the quantitation of the DNA. Real-time
Then each of these molecules is duplicated in aPCR can not only answer the question "what DNA
second cycle of replication, resulting in fouris present?" but also "how much DNA is present?".
molecules. Again, each of these molecules isThe polymerase chain reaction is used by a huge
duplicated by the enzyme in a third cycle ofnumber of scientists in a vast range of scientific
replication. The process is referred to as a chaindisciplines. In microbiology and molecular biology
reaction - hence the name "polymerase chainlaboratories, for example, PCR is used in DNA
reaction". The original single piece of DNA iscloning experiments, genetic manipulation, DNA
amplified over many cycles, generating millions ofsequencing, genetic modification, and many other
copies of the original DNA molecule. Often theprocedures. In clinical diagnostic laboratories PCR is
PCR experiment is performed simply to verifyused for the diagnosis of microbial infections, the
the presence or absence of a particular type ofdetection of hereditary diseases and in
DNA but sometimes PCR is used to generateepidemiological studies. In medicine PCR has led to
sufficient DNA to be used in a subsequentsignificant improvements in the diagnosis of
experiment, for example cloning or DNAinfectious disease. PCR is also used for genetic
sequencing. The original PCR process has beenfingerprinting in forensic and paternity testing
extensively modified to perform a wide array oflaboratories.