http://www.sciencemag.org/news/2019/10/new-prime-genome-editor-could-surpass-crispr > A new way to modify DNA, “prime editor” couples two enzymes, Cas9 (blue) and reverse transcriptase (red), to a guide RNA (green) that takes the complex to a specific place on DNA’s double helix (yellow and purple) and also holds the code for an insertion of new DNA at that spot. > CRISPR, an extraordinarily powerful genome editing tool invented in 2012, can still be clumsy. It sometimes changes genes it shouldn’t, and it edits by hacking through both strands of DNA’s double helix, leaving the cell to clean up the mess—shortcomings that limit its use in basic research and agriculture and pose safety risks in medicine. But a new entrant in the race to refine CRISPR promises to steer around some of its biggest faults. “It’s a huge step in the right direction,” chemist George Church, a CRISPR pioneer at Harvard University, says about the work, which appears online in Nature today.