CRISPR

CRISPR (/ˈkrɪspər/) is a family of DNA sequences in bacteria and archaea.[2] The sequences contain snippets of DNA from viruses that have attacked the prokaryote. These snippets are used by the prokaryote to detect and destroy DNA from similar viruses during subsequent attacks. These sequences play a key role in a prokaryotic defense system,[2] and form the basis of a technology known as CRISPR/Cas9 that effectively and specifically changes genes within organisms.[3]
The CRISPR/Cas system is a prokaryotic immune system that confers resistance to foreign genetic elements such as those present within plasmids and phages[4][5][6] that provides a form of acquired immunity. RNA harboring the spacer sequence helps Cas (CRISPR-associated) proteins recognize and cut exogenous DNA. Other RNA-guided Cas proteins cut foreign RNA.[7] CRISPRs are found in approximately 40% of sequenced bacterial genomes and 90% of sequenced archaea.[8][note 1]
CRISPR is an abbreviation of Clustered Regularly Interspaced Short Palindromic Repeats.[9] The name was minted at a time when the origin and use of the interspacing subsequences were not known. At that time the CRISPRs were described as segments of prokaryoticDNA containing short, repetitive base sequences. In a palindromic repeat, the sequence of nucleotides is the same in both directions. Each repetition is followed by short segments of spacer DNA from previous exposures to foreign DNA (e.g., a virus or plasmid).[10] Small clusters of cas (CRISPR-associated system) genes are located next to CRISPR sequences.
A simple version of the CRISPR/Cas system, CRISPR/Cas9, has been modified to edit genomes. By delivering the Cas9 nuclease complexed with a synthetic guide RNA (gRNA) into a cell, the cell's genome can be cut at a desired location, allowing existing genes to be removed and/or new ones added.[11][12][13] The Cas9-gRNA complex corresponds with the CAS III CRISPR-RNA complex in the above diagram.
CRISPR/Cas genome editing techniques have many potential applications, including medicine and crop seed enhancement. The use of CRISPR/Cas9-gRNA complex for genome editing[14][15] was the AAAS's choice for breakthrough of the year in 2015.[16] Bioethical concerns have been raised about the prospect of using CRISPR for germline editing.[17]
Category:1987 in biotechnology
Category:2015 in biotechnology
Category:Biological engineering
Category:Biotechnology