<p>All proteins in this superfamily for which functions are known are DNA polymerases. DNA-directed DNA polymerase (<db_xref db="EC" dbkey="2.7.7.7"/>) catalyzes DNA-template-directed extension of the 3'-end of an RNA strand by one nucleotide at a time. In eukaryotes there are five DNA polymerases, alpha, beta, gamma, delta and epsilon, which are responsible for different reactions of DNA synthesis. This family includes, among others, the alpha catalytic subunit, which is a replicative polymerase when in a complex with DNA primase, as well as archaeal DNA polymerase.</p>