CRISPRs (clustered regularly interspaced short palindromic repeats) are DNA loci containing short repetitions of base sequences that are present within prokaryotes and function as a primitive immune system, cleaving foreign DNA (from invading viruses). CRISPRs have now been used as gene editing tools in mammalian systems. When paired with the Cas9 nuclease, CRISPRs can cleave genomic DNA in a site-specific manner, thus knocking out gene expression.
The rapid progress in developing Cas9 into a set of tools for cell and molecular biology research has been remarkable, likely due to the simplicity, high efficiency and versatility of the system. Cas9's potential reaches beyond DNA cleavage, and its usefulness for genome locus-specific recruitment of proteins will likely only be limited by our imagination.http://www.cd-genomics.com/CRISPR-Cas9-Sequencing.html