CRISPR was discovered as a bacterial immune system against viruses.

“crisper was being studied as an an interesting and unusual set of DNA sequences that were found in certain types of bacteria. There were these repeated sequences and no one knew what they were. And people out of real basic curiosity about what was happening in bacteria started studying these repeat sequences and what they were doing. And little by little by little it was worked out that these repeat repeat sequences actually ba formed the basis of a kind of immune system for bacteria.”