The Chief Medical Officer for England, Professor Dame Sally Davies, explains that the 'three parent' technique does not tamper with the nucleus. It simply moves it into a cell which has healthy 'battery packs', known as mitochondria, which power the nucleus properly and eradicate serious disease.
More top news
The pensioner, who is in her 70s, says her daughter has suffered from Huntington's disease.
US singer John Legend said he was "moved" by footage of the teenager singing one of his songs.
John Noakes was Blue Peter's longest-serving presenter.