Matt Ridley: CRISPR announcement is great moment in medical history

Baby KJ lacked a working copy of a vital gene

The announcement last week that a nine-month-old baby in Philadelphia has been cured of a rare genetic disorder by gene editing is a great moment in medical history. For the first time, doctors have altered a gene inside many cells in the liver of a living human being using CRISPR, the molecular tool borrowed from microbes that can home in on particular DNA sequences and in some cases alter them.