DNA Polymerase I, Klenow Fragment (Large Fragment) is a proteolytic product of E. coli DNA Polymerase I, which possesses the 5"→3" polymerase and 3"→5" exonuclease activities of intact DNA Polymerase I, but lacksthe 5"→3" exonuclease activity of full-length DNA Polymerase I. The lack of 5"→3" exonuclease activity enables the DNA Polymerase I, Klenow Fragment to be used in random primer labeling and DNAsequencing experiments in addition to second-strand cDNA synthesis. The enzymeis supplied in a buffer of50 mM potassium phosphate (pH 6.5), 1 mmDTT and 50% glyerol (2140A/B) or ethylene glycol (2140AK/BK).