The Basics of CRISPR & How It Works

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The Basics of CRISPR & How It Works

CRISPR lets scientists edit DNA in plants and animals

...CRISPR/Cas9 tool was first described in 2012 and 2013. Science labs around the world soon started using it to alter an organism’s genome — the entire set of its genes.

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CRISPR stands for “clustered regularly interspaced short palindromic repeats.” Those repeats are elements of the genetic code in DNA. Cas9 is an enzyme that can cut apart DNA. Bacteria fight off viruses by wielding the Cas9 enzyme to reorder those repeated genetic segments. Scientists recently figured out how bacteria do this. Now, in the lab, they use a similar approach to turn the microbe’s virus-fighting system into the hottest new lab tool.

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This tool can quickly and efficiently tweak almost any gene in any plant or animal. Researchers already have used it to fix genetic diseases in animals, to combat viruses and to sterilize mosquitoes. They have also used it to prepare pig organs for human transplants and to beef up the muscles in beagles.

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Robert Reed is a developmental biologist at Cornell University in Ithaca, N.Y. He likens CRISPR to a computer mouse. “You can just point it at a place in the genome and you can do anything you want at that spot.”

Anything, that is, as long as it involves cutting DNA. CRISPR/Cas9 in its original form is a homing device (the CRISPR part) that guides molecular scissors (the Cas9 enzyme) to a target section of DNA. Together, they work as a genetic-engineering cruise missile that disables or repairs a gene or inserts something new where the Cas9 scissors has made some cuts.

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How It Works

Scientists cut DNA with CRISPR/Cas9 to make gene changes or mutations. By comparing cells with and without the mutation, scientists can sometimes figure out what a protein’s normal role is. Or a new mutation may help them understand genetic diseases. CRISPR/Cas9 also can be useful in human cells by disabling certain genes — ones, for instance, that play a role in inherited diseases.

“The original Cas9 is like a Swiss army knife with only one application: It’s a knife,” says Gene Yeo. He is an RNA biologist at the University of California, San Diego. But Yeo and others have bolted other proteins and chemicals to the dulled blades. That has transformed that knife into a multifunctional tool.

CRISPR/Cas9 can now be used in new ways, such as changing a single nucleotide base — a single letter in the genetic code — or adding a fluorescent protein to tag a spot in the DNA that scientists want to track. Scientists also can use this genetic cut-and-paste technology to turn genes on or off.

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News Reference: Explainer: How CRISPR works

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