Polymerase Chain Reaction

The polymerase chain reaction (PCR) is a biochemical technology in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence.

Developed in 1983 by Kary Mullis, PCR is now a common and often indispensable technique used in medical and biological research labs for a variety of applications. These include DNA cloning for sequencing, DNA-based phylogeny, or functional analysis of genes; the diagnosis of hereditary diseases; the identification of genetic fingerprints (used in forensic sciences and paternity testing); and the detection and diagnosis of infectious diseases. In 1993, Mullis was awarded the Nobel Prize in Chemistry along with Michael Smith for his work on PCR.

The method relies on thermal cycling, consisting of cycles of repeated heating and cooling of the reaction for DNA melting and enzymatic replication of the DNA. Primers (short DNA fragments) containing sequences complementary to the target region along with a DNA polymerase (after which the method is named) are key components to enable selective and repeated amplification. As PCR progresses, the DNA generated is itself used as a template for replication, setting in motion a chain reaction in which the DNA template is exponentially amplified. PCR can be extensively modified to perform a wide array of genetic manipulations.

Almost all PCR applications employ a heat-stable DNA polymerase, such as Taq polymerase, an enzyme originally isolated from the bacterium Thermus aquaticus. This DNA polymerase enzymatically assembles a new DNA strand from DNA building-blocks, the nucleotides, by using single-stranded DNA as a template and DNA oligonucleotides (also called DNA primers), which are required for initiation of DNA synthesis. The vast majority of PCR methods use thermal cycling, i.e., alternately heating and cooling the PCR sample to a defined series of temperature steps. These thermal cycling steps are necessary first to physically separate the two strands in a DNA double helix at a high temperature in a process called DNA melting. At a lower temperature, each strand is then used as the template in DNA synthesis by the DNA polymerase to selectively amplify the target DNA. The selectivity of PCR results from the use of primers that are complementary to the DNA region targeted for amplification under specific thermal cycling conditions.

Read more about Polymerase Chain ReactionPCR Principles and Procedure, PCR Stages, Variations On The Basic PCR Technique, History

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Biomolecular Engineering of Molecules - Polymerase Chain Reaction - Biomolecular Engineering Techniques Involved in PCR
... Furthermore, as the DNA primer is created certain functional groups of nucleotides to be added to the growing primer require blocking to prevent undesired side reactions ... This blocking of functional groups as well as the subsequent de-blocking of the groups, coupling of subsequent nucleotides, and eventual cleaving from the solid support are all methods of manipulation of biomolecules that can be attributed to biomolecular engineering ...
Digital Polymerase Chain Reaction
... Digital Polymerase Chain Reaction (digital PCR, DigitalPCR, dPCR, or dePCR) is a refinement of conventional polymerase chain reaction methods that can be used to directly quantify and clonally amplify nucleic ... PCR carries out one reaction per single sample ... dPCR also carries out a single reaction within a sample, however the sample is separated into a large number of partitions and the reaction is carried out in each ...
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... The main materials used in polymerase chain reaction are DNA nucleotides, template DNA, primers and Taq polymerase ... are complementary nucleotides that can go on either side of the template DNA, and Taq polymerase is a heat stable enzyme that jump-starts the production of new DNA at the high temperatures needed ...
Polymerase Chain Reaction - History - Patent Wars
... The Taq polymerase enzyme was also covered by patents ... A related patent battle over the Taq polymerase enzyme is still ongoing in several jurisdictions around the world between Roche and Promega ... beyond the lives of the original PCR and Taq polymerase patents, which expired on March 28, 2005 ...
Human Chain
... A human chain is a form of demonstration in which people link their arms as a show of political solidarity ... The number of demonstrators involved in a human chain is often disputed the organizers of the human chain often report higher numbers than governmental authorities ... Notable human chains, in chronological order, have included Date Event Location Number of participants Purpose 1983 Berkshire, England, United Kingdom 40,000 - 80,000 Protested siting of American nuclear missiles ...

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