CRISPR-Cas9 gene editing. Illustration of the process that occurs within the CRISPR-Cas9 gene editing complex. This protein (red) is used in genome engineering to cut DNA (deoxyribonucleic acid). It uses a guide RNA (ribonucleic acid) sequence (yellow) to cut DNA (blue) at a complementary site. Donor DNA (green) can then be inserted into DNA molecule (bottom left). CRISPR (Clustered Regularly Interspersed Palindromic Repeats) is a bacterial adaptive immunity system.