DNA polymerases

DNA polymerase is the essential element of the DNA replication process, in which a double-stranded DNA molecule is copied into two identical DNA molecules. DNA polymerase “reads” the strands of existing DNA to create two new strands that match the existing ones.
DNA polymerase adds new free nucleotides to the 3 ‘end of the newly formed strand, extending it in a 5’ to 3 ‘direction. However, DNA polymerase cannot start the formation of this new chain alone and can only add nucleotides to a preexisting 3’-OH group. A primer is therefore necessary, to which nucleotides can be added. Primers are usually made up of RNA and DNA bases and the first two bases are always RNA. These primers are made by another enzyme called primase.
Although the function of DNA polymerase is very precise, an error is made for approximately one billion base pairs copied. DNA is therefore “corrected” by DNA polymerase after it has been copied so that poorly positioned base pairs can be corrected. This preserves the integrity of the original DNA strand that has passed onto daughter cells.
DNA polymerase is an essential component of PCR because of its key role in the synthesis of new strands of DNA.

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