Until March, the battles were mostly academic because previous attempts to edit human embryos were done in embryos that would never develop into a baby (SN Online: 4/8/16; SN Online: 4/23/15). Instead of using a piece of DNA that the researchers injected to repair cuts made by CRISPR/Cas9, human embryos used their own DNA from another chromosome as a repair template. In October, Liu and colleagues reported that they’d made another base editor that can do a previously impossible trick: convert an A into a G. The two base editors together may allow researchers to repair most of the single base mutations responsible for causing human diseases, such as sickle-cell anemia, muscular dystrophy and cystic fibrosis.