CRISPR Cas9 explained. CRISPR (clustered regularly interspaced short palindromic repeats) are segments of prokaryotic DNA containing short repetitions of base sequences. is an RNA-guided gene-editing platform that makes use of a bacterially derived protein (Cas9) and a synthetic guide RNA to introduce a double strand break at a specific location within the genome.

Cas9 is an enzyme that snips DNA, and CRISPR is a collection of DNA sequences that tells Cas9 exactly where to snip.