A tweak to a technique that edits DNA with pinpoint precision has boosted its ability to correct defective genes in people. Called CRISPR, the method is already used in the lab to insert and remove genome defects in animal embryos. But the genetic instructions for the machinery on which CRISPR relies—a gene-editing enzyme called Cas9 and RNA molecules that guide it to its target—are simply too large to be efficiently ferried into most of the human body’s cells.
Ref: In vivo genome editing using Staphylococcus aureus Cas9. Nature (2015) | DOI:10.1038/nature14299