Polymerase Chain Reaction

PCR - polymerase chain reaction is a method of the DNA replication. It allows us to get a huge number of copies. It is the way how to get the exact part of the DNA strand and use it for a research. PCR is used in gene manipulation.

The correct designation of the section is through the primers. Primer is a nucleotide sequence that binds to the opposite strands of the DNA. We can choose them according to the place of our interest. The primer indicates the start point of the DNA replication by the DNA polymerase. We can produce many types of the primers due to the sequences which we want to study. The samples have to have size from 50 bp to 2,5 kbp.

Process of the PCR
A sample of the DNA has to be heated - the temperature rises from 55oC, throught 70oC to 95oC. Then the double strand DNA is divided into the individual segments and DNA polymerase can start the replication procces. These individual pieces of DNA become a pattern for each copy. The denaturation, the establishment of the primers and the replication are repeated over and over. After 20 cycles we can get about 106 copies, after 30 cycles it is 109.

At first, it was used the polymerase from E.coli. But it is not thermostable enought and it is destroyed after the first heating. So nowadays the polymerase from Thermus aquaticus, which is thermostable, is used.

Use of the PCR

 * 1) in the forensic medicine
 * 2) in prenatal diagnosis
 * 3) in polymorphism detection
 * 4) in study of the evolution
 * 5) in genetic manipulation

Related articles

 * Gene Manipulation
 * Replication
 * DNA polymerase