DNase I is an endonuclease derived from bovine pancreas that will degrade double-stranded DNA in the presence of divalent cations, producing 3”-OH
oligonucleotides. Mg²⁺ in the reaction solution causes the enzyme to produce nicks in double-stranded DNA, while in the presence of Mn²⁺, DNase I cleaves both strands of the DNA.
DNase I is useful in nick translation for introducing single-stranded nicks that serve as primer sites for initiation of DNA synthesis and for cloning random DNA fragments by cleaving double-stranded DNA. DNase I is a chromatographically pure preparation. It is offered as lyophilized powder. For greatest stability, it is important that DNAse be dissolved at a concentration of at least 1mg/ml in 50% Glycerol with 20mM Tris-HCl, pH 7.5 and 1mM MgCl2. This solution can be stored at -20oC for at least a year.