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Thermo Scientific™ Klenow Fragment, exo- Available on GSA/VA Contract for Federal Government customers only.

Klenow Fragment, exo- is the large fragment of DNA polymerase I. Exhibits 5'3' polymerase activity, but lacks the 3'5' and 5'3' exonuclease activities.

Manufacturer:  Thermo Scientific™ EP0422

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Catalog No. FEREP0422

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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 sit.


  • Lacks 3'5' exonuclease activity
  • Incorporates modified nucleotides (e.g., Cy3-, Cy5-, fluorescein-, rhodamine-, aminoallyl-, biotin-labeled nucleotides)
  • Active in restriction enzyme, PCR, and RT buffers


  • Random-primed DNA labeling
  • Labeling by fill-in 5'-overhangs of dsDNA
  • Strand displacement amplification (SDA)
  • DNA sequencing by the Sanger method


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

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E.coli cells with a cloned DNA fragment of the mutated polA gene
metal chelators, PPi, Pi (at high concentrations) (7)
68kDa monomer
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