FAQ: Can T7 DNA Polymerase be used to blunt DNA?

The 3'→5' exonuclease of T7 DNA Polymerase is approximately 1,000X stronger than that of DNA Polymerase I, Large (Klenow) Fragment (NEB# M0210) (1). Therefore, DNA Polymerase I, Large (Klenow) Fragment (NEB# M0210) or T4 DNA Polymerase (NEB# M0203) are recommended for this application. The exonuclease in T4 DNA Polymerase is more robust than that of DNA Polymerase I, Large (Klenow) Fragment and the reaction must be performed at 12°C. DNA Polymerase I, Large (Klenow) Fragment can be used at 25°C or room temperature. Both work well in a wide variety of buffers.
(1) Tabor, S. et al. (1987) J. Biol. Chem., 26, 16212-16223.