Clustered regularly interspaced short palindromic repeats (CRISPRs) and CRISPR-associated (Cas) proteins are found in many bacteria and most archaea. The CRISPR-Cas systems use sequences derived from plasmids and phages to activate Cas endonucleases to neutralize those plasmids and phages via RNA-guided sequence-specific DNA cleavage, thus blocking their transmission and creating a simple acquired immunity.
With their highly flexible but specific targeting, CRISPR-Cas systems can be manipulated and redirected to become powerful tools for genome editing. CRISPR-Cas technology permits targeted gene cleavage and gene editing in a variety of eukaryotic cells, and because the endonuclease cleavage specificity in CRISPR-Cas systems is guided by RNA sequences, editing can be directed to virtually any genomic locus by engineering the guide RNA sequence and delivering it along with the Cas endonuclease to your target cell.