A polymerase is an enzyme (EC that synthesizes long chains or polymers of nucleic acids. DNA polymerase and RNA polymerase are used to assemble DNA and RNA molecules, respectively, by copying a DNA or RNA template strand using base-pairing interactions. It is an accident of history that the enzymes responsible for the generation of other biopolymers are not also referred to as polymerases. For example, the enzymatic complex that assembles amino acids into proteins is termed the ribosome, rather than “protein polymerase”. A polymerase from the thermophilic bacterium, Thermus aquaticus (Taq) (PDB 1BGX, EC is used in the polymerase chain reaction, an important technique of molecular biology. Other well-known polymerases include: Terminal Deoxynucleotidyl Transferase (TDT), which lends diversity to antibody heavy chains Reverse Transcriptase, an enzyme used by RNA retroviruses like HIV, which is used to create a complementary strand to the preexisting strand of viral RNA before it can be integrated into the DNA of the host cell. It is also a major target for antiviral drugs.