Polymerase chain reaction (PCR) - a method of molecular biology, which allows you to discover the biological material in small amounts of deoxyribonucleic acid (DNA), or rather, some of its fragments, and multiply them many times over.Then they were identified visually by gel electrophoresis.Reaction was developed in 1983 by K. Mullis and included in the list of outstanding discoveries of recent years.
What mechanisms PCR
whole technique is based on the ability of nucleic acids to independent replication, which in this case is conducted artificially under laboratory conditions.DNA replication can not begin in any region of the molecule, but only in certain areas with the nucleotide sequence - starting fragments.In order for the polymerase chain reaction has started, the primers need (or DNA probes).This short fragments of DNA strands with a predetermined nucleotide sequence.They are complementary (ie appropriate) start sites of DNA sample.
course to create primers, scientists must study the nucleotide sequence of the nucleic acid, which is involved in the procedure.These DNA probes provide specificity of the reaction and its initiation.Polymerase chain reaction will not go, if the sample does not find at least one molecule of the desired DNA.In general, the reaction requires the above primers, a set of nucleotides, heat resistant DNA polymerase.The latter is an enzyme - catalytic reactions of synthesis of new nucleic acid molecules based on the sample.All of these substances, including biological matter, which is necessary to identify DNA combined in the reaction mixture (solution).It is placed in a special thermostat that performs its very rapid heating and cooling within the specified time - cycle.Usually they are 30-50.
How is this reaction
The essence of it is that during one cycle of the primers are attached to the desired portion of DNA, after which it is doubling by the enzyme.On the basis of the resulting DNA strand synthesized in the subsequent cycles and more identical molecule fragments.
polymerase chain reaction is consistently following its release stage.It characterized by first doubling the amount of product during each cycle of heating and cooling.In the second step of the reaction is slowed down, since the enzyme is damaged and loses activity.In addition, the depleting reserves and nucleotide primers.In the last stage - a plateau - the products are no longer collected as reagents over.
Where it is used
Undoubtedly, the broadest application polymerase chain reaction is in medicine and science.Its use in public and private biology, veterinary medicine, pharmacy, and even the environment.While the latter are doing to monitor food quality and environmental objects.Actively used polymerase chain reaction in the forensic practice to confirm paternity and identification of a person.The forensic medical examination, as well as in paleontology, this technique is often the only way out, as is usually available for research very small amount of DNA.Of course, a very widely used method is found in the practice of medicine.He needs it in such areas as genetics, infectious diseases and cancer.