clustered regularly interspaced short palindromic repeats. They add bits of viral DNA to their own genome to guide the Cas proteins, and the odd patterns of these bits of DNA are what gave CRISPR its name: clustered regularly interspaced short palindromic repeats. CRISPR is a technology that can be used to edit genes and, as such, will likely change the world. So why do we call it CRISPR? Cas proteins are used by bacteria to destroy viral DNA. Yet others, called base editors, change one letter of the DNA code to another. It’s called genome editing – or gene editing – but usually the results are not as precise as that term implies.ĬRISPR can also be used to make precise changes such as replacing faulty genes – true genome editing – but this is far more difficult.Ĭustomised Cas proteins have been created that do not cut DNA or alter it in any way, but merely turn genes on or off: CRISPRa and CRISPRi respectively. This is by far the most common use of CRISPR. When the cut is repaired, mutations are introduced that usually disable a gene. In bacteria, a CRISPR (clustered regularly interspaced short palindromic repeat) locus is a DNA sequence containing direct nucleic acid repeats with. The standard Cas9 protein cuts the DNA at the target. That’s impressive, given that the DNA packed into each of our cells has six billion letters and is two metres long. In the past decade, the widely characterized CRISPR-Cas9 enzyme has been redesigned. When the CRISPR Cas9 protein is added to a cell along with a piece of guide RNA, the Cas9 protein hooks up with the guide RNA and then moves along the strands of DNA until it finds and binds to a 20-DNA-letter long sequence that matches part of the guide RNA sequence. Prokaryotes have developed an adaptive immune system called Clustered regularly interspaced short palindromic repeats (CRISPR) to combat attacks by foreign mobile genetic elements (MGEs) such as plasmids and phages. This protein can easily be programmed to find and bind to almost any desired target sequence, simply by giving it a piece of RNA to guide it in its search. The Cas9 protein is the most widely used by scientists. The key to CRISPR is the many flavours of “Cas” proteins found in bacteria, where they help defend against viruses. An attempt to do this in China has been condemned as premature and unethical, but some think it could benefit children in the future.ĬRISPR is being used for all kinds of other purposes too, from fingerprinting cells and logging what happens inside them to directing evolution and creating gene drives. We may even decide to use it to change the genomes of our children. CRISPR technology also has the potential to transform medicine, enabling us to not only treat but also prevent many diseases.
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