A pioneering technique to ‘fix’ an embryo’s faulty DNA was unveiled by scientists last night. In a world first, they used gene-editing to cut out DNA from a fertilised egg. The embryo then repaired itself, replacing the mutated material with healthy cells. The technique worked on three quarters of the 58 embryos it was tried on. It has the potential to revolutionise medicine and could lead to the eradication of inherited diseases such as cystic fibrosis and breast cancer. Campaigners warned however that it might also open the door to ‘superior designer babies’, with genes modified to improve physical appearance, strength or even intelligence.