CRISPR-Cas9 gene editing complex. Computer illustration showing the molecular structure of the CRISPR-Cas9 gene editing complex from Streptococcus pyogenes. The CRISPR-Cas9 protein is used in genome engineering to cut DNA (deoxyribonucleic acid). It uses a guide RNA (ribonucleic acid) sequence to cut DNA at a complementary site. The Cas9 protein is shown in blue, DNA in red, and single-guide RNA in orange.