 A DNA polymerase from the thermophilic bacterium, "Thermus aquaticus" ("Taq") (PDB 1BGX, EC 2.7.7.7) is used in the polymerase chain reaction, an important technique of molecular biology.In general, viral single-subunit RNA polymerases/replicases/reverse transcriptase shares a common origin with DNA polymerase.They have a conserved "palm" domain.