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On 26 November 2018, The CRISPR Journal published ahead of print an article by He, Ryan Ferrell, Chen Yuanlin, Qin Jinzhou, and Chen Yangran in which the authors justified the ethical use of CRISPR gene editing in humans. [74] As the news of CRISPR babies broke out, the editors reexamined the paper and retracted it on 28 December, announcing:
CRISPR gene editing (CRISPR, pronounced / ˈ k r ɪ s p ə r / (crisper), refers to a clustered regularly interspaced short palindromic repeats") is a genetic engineering technique in molecular biology by which the genomes of living organisms may be modified.
Off-target genome editing refers to nonspecific and unintended genetic modifications that can arise through the use of engineered nuclease technologies such as: clustered, regularly interspaced, short palindromic repeats ()-Cas9, transcription activator-like effector nucleases (), meganucleases, and zinc finger nucleases (ZFN). [1]
The different generations of nucleases used for genome editing and the DNA repair pathways used to modify target DNA. Genome editing, or genome engineering, or gene editing, is a type of genetic engineering in which DNA is inserted, deleted, modified or replaced in the genome of a living organism.
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.
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.
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.
CRISPR interference (CRISPRi) is a genetic perturbation technique that allows for sequence-specific repression of gene expression in prokaryotic and eukaryotic cells. [1] It was first developed by Stanley Qi and colleagues in the laboratories of Wendell Lim , Adam Arkin, Jonathan Weissman , and Jennifer Doudna . [ 2 ]