Reaction mixtures (20 µl) containing 50 mM Tris-HCl (pH 8.0), either 1 pmol of 32P-labeled primer-template DNA substrate (panel A), 1 pmol of 32P-labeled blunt duplex DNA substrate (panel B), or 1 pmol of 32P-labeled single-strand primer (panel C), 100 µM each of dATP, dGTP, dCTP and dTTP (dNTPs) or 100 µM each of ATP, GTP, CTP and UTP (rNTPs), 200 ng MsmPolD2, and either no added metal (lanes –) or 1.25 mM of the indicated divalent cations were incubated for 10 min at 37°C. The reaction products were resolved by PAGE and visualized by autoradiography.