DNA replication, recombination and repair, all of which are necessary for genomic stability, require the presence of exonucleases. In DNA replication, these enzymes are involved in the processing of Okazaki fragments, whereas in DNA repair, they function to excise damaged DNA fragments and correct recombinational mismatches. These exonucleases include the family of DNA polymerases (DNA pol). DNA pol Alpha, Beta, Gamma, and epsilon are involved in DNA replication and repair. DNA pol gamma and DNA pol e are multi-subunit enzymes, with DNA pol gamma consisting of two subunits: p125, which interacts with the sliding DNA clamp protein, PCNA, and p50. The nuclear-encoded DNA pol Delta is the only DNA polymerase required for the replication of the mitochondrial DNA. DNA pol zeta is ubiquitously expressed in various tissues and mediates the cellular mechanism of damage-induced mutagenesis. DNA pol theta is a DNA polymerase-helicase that binds ATP and is involved in the repair of interstrand crosslinks.