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~ Crispr/cas9 ~

CRISPR is a molecule that finds a string of DNA code, locks on and makes a precision cut. And because scientists can tune it to target any genetic sequence, they can use it to turn genes off or replace them with new versions.

CRISPR" (pronounced "crisper") stands for Clustered Regularly Interspaced Short Palindromic Repeats, which are the hallmark of a bacterial defense system that forms the basis for CRISPR-Cas9 genome editing technology.

CRISPR evolved in simple, single-celled microbes as a weapon for fighting off viruses. When viruses attack a bacterial cell, for instance, they inject a payload of their own DNA into the cell. The cell responds by deploying CRISPR, which consists of a strand of ribonucleic acid, or RNA, hooked up to an enzyme called CRISPR associated protein, or Cas. The RNA is primed to recognise and dock to the virus DNA, neatly encasing it in a pocket of the Cas enzyme. Cas, in turn, makes a cut in the DNA, which disables the virus' attack.

Since 2012 scientists have tinkered with the CRISPR system in the lab to target not virus DNA, but genes in animal or plant cells. CRISPR alone can disable or "knock out" genes in cells. And if a strand of DNA coding for a new gene is added to the mix, CRISPR can be used to patch in a new gene between the chopped ends.

The recipe is fairly simple: a researcher designs and orders a piece of RNA that locks on to whatever gene they're interested in, mixes it up with some Cas enzyme and voilà – they have cooked up their own customised precision gene-editing tool.

Who would have thought our most advanced gene-editing tool would be carbon-copied from one of the most primitive life forms on Earth?

But since 2012 the CRISPR molecule, which was first discovered in bacteria, has rapidly found its way into the pipettes of researchers everywhere.

It is faster, cheaper and more accurate than previous methods of tinkering with the genetic code. And with applications in treating human disease, agriculture – even designer babies – it's no wonder the technology has created a storm of controversy. It has set us on the doorstep of a genetic revolution.

More on CRISPR:
CRISPR Pioneer Feng Zhang Talks About What's Next for Gene Editing
CRISPR/Cas9 and Targeted Genome Editing: A New Era in Molecular Biology
Scientists are debating the ethics and future of the genome-editing tool that has taken the global scientific community by storm Libraries of tens of thousands of guide RNAs are available.

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