Every year, thousands of people die because of typos in their genes. There’s a long list of debilitating or fatal genetic diseases that are caused by a single incorrect DNA letter among the three billion in our genome. It’s the equivalent of pulping an entire encyclopaedia on the basis of a single typo. But hope is at hand. We are fast approaching the point when we can proofread these errors out of our genes.

Kosuke Yusa  and Tamir Rashid have taken the latest step towards this goal, by developing a more efficient and less risky way of correcting genetic errors. They took cells from patients with a genetic liver disease, edited the gene responsible, and grew corrected liver cells that successfully