DNA Polymerase I is a DNA polymerase with 5´→3´ and 3´→5´ exodeoxyribonuclease activities. DNA Polymerase I also incorporates biotinylated nucleotides.

• Applications—DNase I-dependent nick translation, second-strand synthesis in cDNA cloning, fill-in of 5´ overhangs
• Source—purified from E. coli expressing the DNA Polymerase I gene on a plasmid

Performance and quality testing
Endodeoxyribonuclease assay; efficiency of DNase I-dependent nick translation determined.

Unit definition
One unit incorporates 10 nmol of total deoxyribonucleotide into acid-precipitable material in 30 min at 37°C using template/primer.

Unit reaction conditions
50 mM potassium phosphate (pH 7.0), 6.7 mM MgCl₂ , 1 mM 2-mercaptoethanol, 80 μg/mL template/primer, 32 μM dTTP, 69 nM [³H]dTTP, and enzyme in 100 μL for 30 min at 37°C.