T4 DNA Polymerase catalyzes the 5'–>3' incorporation of nucleotides into double-stranded DNA using single-stranded and primed DNA as a template. It possesses strong 3'–>5' exonuclease (proofreading) activity but does not exhibit 5'–>3' exonuclease activity. Typical T4 DNA polymerase protocols include 5' DNA overhang blunting as well as the generation of blunt double-stranded DNA from double-stranded DNA containing 3' overhangs. These DNA products are often used in blunt cloning. T4 DNA Polymerase is supplied in a buffer of 200 mM potassium phosphate (pH 6.5), 10 mM DTT and 50% glycerol.