DNA Polymerases

DNA polymerases are proteins that synthesize new DNA strands using preexisting DNA strands as templates. Before one cell divides to produce two cells, the DNA containing the genetic information in it must be duplicated for the new cell, in a process known as polymerization. In human cells, duplicating the DNA genome requires the polymerization of 2.91 billion nucleotides, the building blocks of DNA. In the bacterium Escherichia coli, the polymerization of 4.64 million nucleotides is necessary to duplicate the genome for the new cell. In all cells, the DNA polymerases are the protein catalysts that link together the nucleotide building blocks of the new DNA polymer in an accurate and timely process that occurs during replication.

The DNA polymerases are also required to repair the DNA of the genome. The genome's DNA can be damaged by highly reactive molecules that are either produced in the cell during normal metabolic processes or brought into the cell from external sources. The damage, if not repaired, could result in the production of mutations in the genome or possibly cell death. Several DNA repair processes occurring in the cell have been identified that preserve the integrity of the genome by removing the damaged nucleotides and resynthesizing DNA by the DNA polymerases.