The fragment of Escherichia coli DNA polymerase I derived by removal of the 5â€²â€“3â€² exonuclease domain. It has the function of adding bases to the unpaired stretch of DNA at the end of a growing DNA duplex.
The large fragment of E. coli DNA Polymerase I. The Klenow fragment retains DNA polymerase activity and 3'-5' exonuclease activity, and is used for DNA sequencing.
The Escherichia coli DNA polymerase, without the exonuclease subunit.