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One of the risks of CRISPR/Cas9 genome editing is the repetitive DNA editing event after the initial process has worked. When the Cas9 nuclease and the guide RNA are introduced as DNA vectors, sustained expression of these vectors may cause repetitive DNA repair and also increase the risk of off-target genome editing. Delivering Cas9 and guide RNA as RNA molecules provides the adjustment of half-life of these molecules, thus limiting the unwanted effects of the Cas9 nuclease.