abbreviation for Clustered Regularly Interspaced Short Palindromic Repeats. The CRISPR/Cas system is found in bacteria and serves as a sort of bacterial immune system for removing foreign DNA elements such as bacteriophage. CRISPR/Cas elements are segments of prokaryotic DNA containing short repetitions of nucleic acids. Each repetition is followed by short segments of “spacer DNA” from previous exposures to a bacterial virus or plasmid. Since 2013, the CRISPR/Cas system has been used for gene editing (adding, disrupting or changing the sequence of specific genes) and gene regulation. CRISPR can allow the organism’s genome to be edited at any desired location.