Researchers in China have used a procedure described as "chemical surgery" to mend harmful mutations in human embryos for the first time.

The scientists found that it was possible to repair a faulty gene that gives rise to a serious blood disorder called beta thalassemia which can be caused by one misspelling in the DNA code.

None of the embryos treated in the experiments were used to produce babies, and doing so would be illegal in the UK and many other countries. But the work proves that the method, known in genetics as "base editing", could be an effective way to prevent inherited diseases. Base editing was dubbed "chemical surgery" by its inventor, David Liu at Harvard University.

In the past decade, scientists have developed a range of powerful tools to edit the genetic code, the most popular of which is called Crispr-Cas9. The method uses enzymes to make precision cuts in faulty genes which the body can then repair with the correct DNA.