Q: Where do CRISPRs come from? A: CRISPRs were first discovered in archaea (and later in bacteria) by Francisco Mojica, a scientist at the University of Alicante in Spain. He proposed that CRISPRs serve as part of the bacterial immune system, defending against invading viruses.

Where do CRISPRs naturally occur?

CRISPR-Cas9 was adapted from a naturally occurring genome editing system in bacteria. The bacteria capture snippets of DNA from invading viruses and use them to create DNA segments known as CRISPR arrays. The CRISPR arrays allow the bacteria to "remember" the viruses (or closely related ones).

How is CRISPR made?

They are copied from the genetic material of viruses that infect bacteria. When a bacterium encounters a virus that it was previously exposed to, it produces an RNA copy of the CRISPR that contains that virus' genetic information. The RNA then guides an enzyme, called Cas9, to cut up the virus and make it harmless.