A genetic disease has been cured in living, adult animals for the first time using a revolutionary genome editing technique that can make the smallest changes to the vast data base of the DNA molecule with pinpoint accuracy. Scientists have used the genome editing technology to cure adult lab. Mice of an inherited liver disease by correcting a single “letter” of the genetic alphabet which has been mutated in a vital gene involved in liver metabolism. A similar mutation in the same gene causes the equivalent inherited liver disease in humans – and the successful repair of the genetic defect in lab. Mice raise hopes that the first clinical trials on patients could begin within a few years. The success is the latest achievement in the field of genome editing. This has been transformed by the discovery of crispr, a technology that allows scientists to make almost any DNA changes at precisely defined points on the chromosomes of animals or plants crispr – pronounced “crisper” – was initially discovered in 1987 as an immune defence used by bacteria against invading viruses. It is powerful genome editing potential in higher animals, including humans, was only fully realized in 2012 and 2013 when scientists showed that it can be combined with a DNA – sniping enzyme called Cas9 and used to edit the human genome. Since then there has been an explosion of interest in the technology because it is such a simple method of changing the individual letters of the human genome – the 3 billion “base pairs” of the DNA molecule – with an accuracy equivalent to correcting a single misspelt word in a 23-volume encyclopaedia.