Wolf, J.M. et. al. (2016) PNAS https://www.ncbi.nlm.nih.gov/pubmed/27956611
While CRISPR gene editing is more efficient than older technologies, such as Zinc Finger Endonucleases and TALENs, screening for desired insertions/deletions continues to limit the pace of CRISPR experiments. To overcome this bottleneck, Wolf et al. fused Cas9 with TevI to create a dual nuclease that allows for biasing of deletions to precise lengths. The length of the deletion created can be controlled by varying the length of the spacer separating Cas9 and TevI creating a system that can be modified for different lengths of deletions.