The CRISPR genome-editing technologies are based on an antiviral defense system that operates in bacteria. This biological system can be utilized in, for example, human cells to target a gene of interest by expressing a gRNA with homology to that gene’s sequence. The gRNA is used to direct the CAS9 DNA nuclease to a specific position in the genome, resulting in a double strand break. Imprecise repair of the Cas9-mediated cut in the DNA results in small insertion or deletions, leading to frame-shift and premature termination of translation. With this iit is possible to generate cells that no longer express the protein of interest (knockout). Moreover, libraries of gRNAs that each target a specific gene can be used to screen for genes involved in a specific biological process or phenotype.