Thermo Scientific™

Klenow Fragment, exo– (5 U/µL)

Catalog number:  EP0421

Related applications:

Nucleic Acid Labeling & Oligo Synthesis

| DNA Sequencing

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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.


• 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.
For Research Use Only. Not for use in diagnostic procedures.


Quantity: 300U
Polymerase: DNA Polymerase I