OTC and urea cycle: In a new study, researchersused dual adeno-associated virus (AAV) vectorsto deliver the CRISPR/Cas9 components, oneexpressing Cas9 and the other expressing a guideRNA as well as the donor DNA, to newborn micewith a partial deficiency in the urea cycle disorderenzyme, ornithine transcarbamylase (OTC),which resulted in improvment of their survivalrate.