Perpetual OptiTaq PCR Master Mix (2x) is a ready-to-use solution containing Perpetual OptiTaq DNA Polymerase, optimized reaction buffer, MgCl₂ and dNTPs. Use of Perpetual OptiTaq PCR Master Mix (2x) allows to save time and reduce contamination risk due to fewer pipetting steps during PCR set-up. Perpetual OptiTaq DNA Polymerase is a modified and balanced blend containing top quality Thermus aquaticus DNA Polymerase, Pyrococcus sp. DNA Polymerase and anti-TaqDNA Polymerase antibodies. Anti-Taq antibodies inhibit polymerase activity at temperatures up to 70°C. The polymerase activity is restored during the initial denaturation step when amplification reactions are heated at 92-95°C for two minutes. Formation of inactive complexes between Taq DNA Polymerase and an anti-Taq antibody forms a basis for automatic “hot start” PCR, which allows for the assembly of PCR reactions at room temperature. “Hot start” PCR may increase specificity, sensitivity and yield of a PCR reaction in comparison to the conventional PCR assembly method. The enzymes blend exhibits the 3‘→5‘ proofreading activity, resulting in considerably higher PCR fidelity and processivity than possible with unmodified Taq DNA polymerase. Enables increased amplification product yield in comparison with Taq DNA polymerase over wide range of PCR products. Perpetual OptiTaq PCR Master Mix (2x) is recommended for use in PCR and primer extension reactions at elevated temperatures to obtain a wide range of DNA products up to 20 kb.