Thermo Scientific Klenow Fragment, exo-, is the large fragment of DNA polymerase I . It exhibits 5'→3' polymerase activity, but lacks the 3'→5' and 5'→3' exonuclease activities of DNA Polymerase I. The 3'→5' exonuclease activity of the enzyme is eliminated by mutations in the 3'→5'-exonuclease active site ( see Reference1).
Klenow Fragment, exo- is not recommended for DNA blunting reactions prior to DNA ligation since it frequently adds one or more extra nucleotides to the 3'-terminus of blunt-end DNA substrates in a non-template directed fashion ( see Reference8).
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