DNA polymerase

DNA polymerases are a family of enzymes responsible for catalysing DNA-dependent DNA-synthesis, more simply known as DNA replication.

There are many types of polymerase, some described below.

In bacteria, there are three types of DNA polymerase: I, II and III.

  • ´╗┐DNA polymerase I fills the gaps between Okazaki fragments of the lagging strand, as well as removing the primer at the start of DNA replication and replacing it with nucleotides. DNA pol I also has a major gap-filling role in DNA repair.

  • DNA polymerase II is primarily involved in the SOS response to DNA damage

  • DNA polymerase III is the primary enzyme of DNA replication. Various subunits (a, e, and q) ´╗┐form the core polymerase while other subunits prevent the enzyme from falling off its template.

In mammals, five types of DNA polymerase have been identified: a, b, g, d, and e. While g is found only in the mitochondria, where it is responsible for mitochondrial DNA (mtDNA) replication. The other polymerases have the following roles:

  • a: synthesis of lagging strand.
  • b: DNA repair.
  • d: synthesis of leading strand.
  • e: DNA repair.