CRISPR-Cas13 gene editing complex, molecular structure. The CRISPR-Cas13 protein is used in genome engineering to cut DNA (deoxyribonucleic acid). It uses a guide RNA (ribonucleic acid) sequence (red) to cut DNA at a complementary cleavage site. It is a type VI-D CRISPR-Cas effector (an RNA-guided ribonuclease) that has been re-purposed to edit RNA in a programmable manner. The coding sequence for Cas13d is small enough to fit within the packaging limits of adeno-associated viruses (AAV) for in-vivo delivery.