CRISPR (Clusters of Regularly Interspaced Short Palindromic Repeats) loci and cas (CRISPR-associated) genes provide adaptive immunity (see panel below) in bacteria and have recently been repurposed for genome editing.
Systems are structurally and functionally diverse. 2 classes, 6 types, 33 subtypes Very few have been studied experimentally None of the Type IV systems have been characterize
