DNase I stock solutions

DNase I stock solutions are stored at -2O C (1 mg/ml) in 5- xl aliquots (each aliquot is used once). Variation in the activity of DNase I preparations is often observed and the exact amount needed to introduce the desired number of nicks should be determined for each enzyme batch. Sometimes template switches occur which will result in snap-back structures (zero-binding nucleic acid), which remain S, nuclease-resistant upon denaturation. Rigby et al. (1977) suggested that this effect was due to a differential loss of 5 - 3 exonuclease activity upon storage leading to a displacement of the nicked strand and a template switch from the complementary... 

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