CRISPRs (clustered regularly interspaced short palindromic repeats) are segments of prokaryotic DNA containing short repetitions of base sequences. Each repetition is followed by short segments of "spacer DNA" from previous exposures to a bacterial virus or plasmid.[2] It is pronounced "crisper".[3]
The CRISPR/Cas system is a prokaryotic immune system that confer resistance to foreign genetic elements such as plasmids and phages,[4][5] and provides a form of acquired immunity. CRISPR spacers recognize and cut these exogenous genetic elements in a manner analogous to RNAi in eukaryotic organisms.[2] CRISPRs are found in approximately 40% of sequenced bacteria genomes and 90% of sequenced archaea.[6][note 1]
The CRISPR/Cas system has been used for gene editing (adding, disrupting or changing the sequence of specific genes) and gene regulation in species throughout the tree of life.[7] By delivering the Cas9 protein and appropriate guide RNAs into a cell, the organism's genome can be relatively cheaply cut at any desired location.[8][9][10]
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