Computer illustration showing the molecular structure of the CRISPR-associated protein Cas9 in complex with RNA (ribonucleic acid, red) and DNA (deoxyribonucleic acid, orange-fuchsia). Cas9 is a nuclease protein associated with the CRISPR (Clustered Regularly Interspersed Palindromic Repeats) adaptive immunity system in Streptococcus pyogenes and other bacteria. It uses a guide RNA sequence to cut DNA at a complementary site. Seen here: Cas9 alpha-helical lobe (grey), HNH domain (blue), RuvC domain (light blue), C-terminal-domain (pink), topo homology domain (pale pink), arginine-rich helix (light fuchsia), guideRNA (red), target DNA (orange), non-target DNA (fuchsia). | Ramon Andrade 3DCiencia/Science Photo Library/Getty Images

CRISPR DNA Editing Can Cause Hundreds of Off-Target Mutations

A new study offers a cautionary tale for using the widely hyped gene-editing tool CRISPR on people.