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The CRISPR-Cas9 system has been shown to make effective gene edits in Human tripronuclear zygotes, as first described in a 2015 paper by Chinese scientists P. Liang and Y. Xu. The system made a successful cleavage of mutant Beta-Hemoglobin in 28 out of 54 embryos. Four out of the 28 embryos were successfully recombined using a donor template.
The CRISPR/Cas (clustered regularly interspaced short palindromic repeats/CRISPR associated nucleases) system was originally discovered to be an acquired immune response mechanism used by archaea and bacteria. It has since been adopted for use as a tool in the genetic engineering of higher organisms.
CRISPR-Cas9 genome editing techniques have many potential applications. The use of the CRISPR-Cas9-gRNA complex for genome editing [10] was the AAAS's choice for Breakthrough of the Year in 2015. [11] Many bioethical concerns have been raised about the prospect of using CRISPR for germline editing, especially in human embryos. [12]
CRISPR [43] is the leading genetic engineering method. [44] In 2014, Esvelt and coworkers first suggested that CRISPR/Cas9 might be used to build gene drives. [ 5 ] In 2015, researchers reported successful engineering of CRISPR-based gene drives in Saccharomyces [ 45 ] , Drosophila , [ 46 ] and mosquitoes .
Designer nuclease systems such as CRISPR-cas9 are becoming increasingly popular research tools as a result of their simplicity, scalability and affordability. [10] [11] With this being said, off-target genetic modifications are frequent and can alter the function of otherwise intact genes. Multiple studies using early CRISPR-cas9 agents found ...
Targeted gene knockout using CRISPR/Cas9 requires the use of a delivery system to introduce the sgRNA and Cas9 into the cell. Although a number of different delivery systems are potentially available for CRISPR, [37] [38] genome-wide loss-of-function screens are predominantly carried out using third generation lentiviral vectors.
See: Guide RNA, CRISPR. Complementary base pairing between the sgRNA and genomic DNA allows targeting of Cas9 or dCas9. A small guide RNA (sgRNA), or gRNA is an RNA with around 20 nucleotides used to direct Cas9 or dCas9 to their targets. gRNAs contain two major regions of importance for CRISPR systems: the scaffold and spacer regions.