This animation created with cryo-EM structures depicts the pathway of the CRISPR Cas9 enzyme as it cuts DNA for gene editing. Animation courtesy of Xing Zhu, Miljan Simonovic and Sriram Subramaniam.

FREDERICK, Md. -- CRISPR is one of the most widely used technologies in the nascent quest to edit the human genome, and the precision “instrument” that makes it so effective is Cas9, a programmable enzyme harnessed from bacterial cells that cuts DNA strands at specific targets and replaces one gene with another.