Taq polymerase ("Taq pol") is a thermostable polymerase isolated from Thermus aquaticus, a bacterium that lives in hot springs and hydrothermal vents. "Taq polymerase" is an abbreviation of Thermus Aquaticus Polymerase. It is often used in polymerase chain reaction, since it is reasonably cheap and it can survive PCR conditions. Its halflife at 95 degrees Celsius is 1.6 hours. Unfortunately, it doesn't have a very high fidelity since it lacks the 3' --> 5' exonuclease proofreading capacity to replace an accidental mismatch in the newly synthesized DNA strand. Commerically sold Taq DNA polymerase has an error rate of one in 8 million nucleotides and typically produces 16% of mutated 1kb (kilobasepair) PCR products in a reaction. As a result, Taq is rarely used for molecular cloning of PCR fragments and is now typically used for checking for the presence and size of a PCR amplified product. It can amplify a 1kb strand of DNA in 30 to 60 seconds at 72°C. Taq DNA polymerase also yields fragments with A overhangs.