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- DictionaryCRISP·R/ˈkrispər/
noun
- 1. a segment of DNA containing short repetitions of base sequences, involved in the defense mechanisms of prokaryotic organisms to viruses.
CRISPR-Cas immunity is a natural process of bacteria and archaea. CRISPR-Cas prevents bacteriophage infection, conjugation and natural transformation by degrading foreign nucleic acids that enter the cell. Spacer acquisition
- CRISPR
- Escherichia coli
- Overview
- Natural defense system
- Role in gene editing
- Applications of CRISPR technology
- Ethical considerations
CRISPR, short palindromic repeating sequences of DNA, found in most bacterial genomes, that are interrupted by so-called spacer elements, or spacers—sequences of genetic code derived from the genomes of previously encountered bacterial pathogens. CRISPR elements are found naturally in many bacteria and archaea, where they provide a sort of genetic ...
As a naturally occurring adaptive defense system, CRISPR functions by destroying nucleic acids from pathogens that invade the cell. The effectiveness and efficiency of CRISPR immunity is directly linked to the presence of spacer elements. Spacer elements essentially are recognition sequences that match sequences in pathogen genomes; as spacers from newly encountered pathogens are added to the bacterial genome, the cell gains the ability to recognize those pathogens on repeat encounters. Most new spacer elements are inserted only at one end of the CRISPR region; hence, across the length of the CRISPR region exists a record of pathogens that have been encountered by the cell and its ancestors over time. Less often, spacers are added in other places in a process called ectopic integration.
The CRISPR system works by producing small “guide RNA” sequences that correspond to specific DNA targets. Guide RNAs, generated via transcription of the CRISPR region, include hairpin formations, derived from the palindromic repeats, that are linked to sequences derived from the spacer elements. When guide RNAs bind to their DNA targets, an RNA-DNA heteroduplex is formed. The heteroduplex binds to a nuclease called CRISPR-associated (Cas), which catalyzes the cleavage of double-stranded DNA at a position near the junction of the target-specific sequence and the palindromic repeat in the guide RNA. In this way, the nuclease destroys invading pathogenic genomes.
The high sequence specificity of the CRISPR system has drawn significant interest in the field of gene editing. The functional precision of CRISPR allows researchers to remove and insert DNA in desired locations within a genome, making it possible to correct genetic defects in animals and to modify DNA sequences in embryonic stem cells. These types of sequence corrections and alterations are possible because RNA-DNA heteroduplexes are stable and because designing an RNA sequence that binds specifically to a unique target DNA sequence is based simply on the Watson-Crick base-pairing rules (adenine binds to thymine [or uracil in RNA], and cytosine binds to guanine).
The possibility of using CRISPR as a gene-editing technology was recognized in 2012 by American scientist Jennifer Doudna, French scientist Emmanuelle Charpentier, and colleagues. These researchers discovered that guide RNAs produced by CRISPR bind to nucleases, which then target particular DNA sequences, and that such RNAs could be modified to bind to a desired sequence. The researchers found that the type II CRISPR-Cas9 system was especially versatile for correcting or altering desired target sequences. Doudna and Charpentier shared the 2020 Nobel Prize in Chemistry for their work.
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CRISPR gene-editing technology has a wide array of research and medical applications. For example, in the laboratory, CRISPR systems can be used to modify genes in bacteria and in animal and plant models, enabling researchers to gain new understanding of the effects of genetic modification. Although preexisting genetic engineering technologies have allowed researchers to investigate various types of genetic modifications and alterations for decades, CRISPR is less costly, more efficient, and more reliable.
In addition, different CRISPR-based therapies are being explored in clinical trials for the treatment of certain human diseases. Some examples include novel treatments for diabetes; for sickle cell disease; for cancers of blood-forming tissues, such as multiple myeloma, leukemia, and lymphoma; for chronic infectious diseases, such as AIDS; and for a form of inherited impairment in vision known as Leber congenital amaurosis. Investigations of CRISPR-based therapies in humans are helping to shed light on how DNA alterations induced by CRISPR enzymes affect cells, on how the human immune system responds to CRISPR-derived interventions, and on risks associated with unwanted off-target alterations in DNA.
The ability to easily and accurately edit genes using CRISPR technology has raised significant ethical issues. In particular, CRISPR can be used to modify DNA sequences in embryonic stem cells, such as in germ-line (sperm and egg) genome modification in humans. Critics point out that this ability, applied to embryos in the womb, may be used to improve traits such as intelligence, appearance, and athletic ability, potentially introducing permanent changes in human DNA. The generation of such “designer babies” sparked debates about the morality of tampering with human development and the ethics of who would have access to the technology. The world’s first gene-edited human babies were born in late 2018 in China; the infants, twin girls, carried an edited gene that reduced the risk of HIV infection.
Following the birth of gene-edited babies, some medical and bioethics researchers, including Charpentier, called for a moratorium on editing human genes in eggs, sperm, or embryos. They contend that because there remain many unknowns about the technology, scientists may unintentionally introduce as many genetic errors as they attempt to fix. Nonetheless, critics argue that CRISPR technology is a remarkable achievement with significant potential to improve human health, although under rigorously controlled conditions.
CRISPR is a way of finding and altering a specific bit of DNA inside a cell. It can be used for scientific research, medicine, agriculture and more, but also raises ethical and environmental concerns.
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3 days ago · Definition. CRISPR (short for “clustered regularly interspaced short palindromic repeats”) is a technology that research scientists use to selectively modify the DNA of living organisms. CRISPR was adapted for use in the laboratory from naturally occurring genome editing systems found in bacteria.
CRISPR is a bacterial defense system that can be used to alter genetic material (DNA) in living cells. Learn how CRISPR works, what it can do and what clinical trials are testing it for.
Mar 13, 2023 · CRISPR is a powerful tool for editing genomes, meaning it allows researchers to easily alter DNA sequences and modify gene function. It has many potential applications, including correcting ...
Jul 31, 2017 · CRISPR is a bacterial system that can cut and edit DNA in plants and animals. Learn how scientists use CRISPR/Cas9 and related tools to study and manipulate genes, and what are the applications and challenges of this technique.
