Invitrogen sells the native form of the Taq DNA polymerase and a cloned version that is expressed in E. coli. Both will leave a 3' dA overhang on ~30% of the ends of PCR fragments).
Taq DNA Polymerase catalyzes the incorporation of dNTPs into DNA. It requires a DNA template, a primer terminus, and the divalent cation Mg++. Taq DNA Polymerase contains a polymerization dependent 5'-3' exonuclease activity. It does not have a 3'-5' exonuclease and thus no proof reading function. Despite this, the enzyme synthesizes DNA in vitro with reasonable fidelity.
In repeated use for cycle sequencing, it has shown no tendency to misincorporate nucleotides. The recombinant Taq DNA Polymerase expressed in E. coli shows identical characteristics to native Taq from Thermus aquaticus with respect to activity, specificity, thermostability and performance in PCR.
Taq DNA Polymerase is supplied with a 10X Taq Reaction buffer (200 mM Tris pH 8.4, 500 mM KCl) and a tube of 50 mM MgCl2. The buffer/MgCl2 is also sold separately.