How do polymerases work

In the case of DNA polymerase, the degree of processivity refers to the average number of nucleotides added each time the enzyme binds a template. This results in elongation of the newly forming strand in a 5'-3' direction.

No known DNA polymerase is able to begin a new chain; it can only add a nucleotide onto a pre-existing 3'-OH group, and needs a primer at which it can add the first nucleotide. Since DNA polymerase requires a free 3' OH group for initiation of synthesis, it can synthesize in only one direction by extending the 3' end of the preexisting nucleotide chain. Hence, DNA polymerase moves along the template strand in a 3'-5' direction, and the daughter strand is formed in a 5'-3' direction.

This difference enables the resultant double-strand DNA formed to be composed of two DNA strands that are antiparallel to each other.

Extending — when the temperature is raised and the new strand of DNA is made by the Taq polymerase enzyme. These three stages are repeated times, doubling the number of DNA copies each time. A complete PCR reaction can be performed in a few hours, or even less than an hour with certain high-speed machines. After PCR has been completed, a method called electrophoresis can be used to check the quantity and size of the DNA fragments produced.

Related Content:. What is DNA replication? What is DNA? What is a gene? What is DNA sequencing? How helpful was this page? What's the main reason for your rating? Which of these best describes your occupation? DNA polymerase is thought to be able to replicate nucleotides per second. By the end of the replication process two new DNA molecules will have been made, each identical to the other and to the original parent molecule.

Such accurate replication is helped by the fact that DNA polymerase has an inbuilt capacity to detect and correct any mistakes it makes in the replication process. Several families of DNA polymerases have now been identified and new ones are continuing to be discovered.

Some of the most useful polymerases for biotechnology are those classified in families labelled A and B. These tend to be single subunit polymerases. Genetic engineering is also adding tailor-made polymerases to the repertoire.

They have also facilitated the development of whole genome amplification and the generation of next generation sequencing tools.

Respond to or comment on this page on our feeds on Facebook , Instagram or Twitter. Facebook Twitter Donate to WiB. It was achieved by Arthur Kornberg, an American biochemist, and his colleagues while studying Escherichia coli, a type of bacteria. The discovery that DNA polymerase, an enzyme, could replicate DNA was a major breakthrough because up to this point most scientists believed it was not possible for scientists to duplicate the genetic specificity that is required for DNA replication outside of an intact cell.

Kornberg's work opened the way to the discovery of many other similar enzymes and the development of recombinant DNA. Donate Facebook Twitter. Kornberg , Bessman, Simms, Lehman. Washington University in St.