The use of gene editing to eliminate diseases has numerous challenges, including the not-so-small problem of dealing with mutation-based conditions like Huntington's. Existing approaches that replace the gene could cause damage. Salk Institute scientists say they've created a tool that can perform edits when mutations are at work. SATI (Single homology Arm donor mediated intro-Targeting Integration) builds on HITI, a variant of the familiar CRISPR-Cas9 gene editing technique, deals with mutations by inserting a healthy copy of a troublesome gene into the non-coding region of DNA. As the DNA repairs itself, the normal gene integrates into the genome alongside the old one -- it eliminates the harm from the mutation without taking risks.