A fertility treatment which eliminates hereditary disease by engineering babies to carry healthy DNA from a third biological parent could be legalised next year. Members of the public are being asked whether families with a genetic risk of incurable conditions like muscular dystrophy should be allowed to use the DNA of a third party to create healthy children. Although the resulting babies would inherit a small fraction of their DNA from the donor and not their mother or father, the procedure would spare all future generations from a host of rare and debilitating conditions. The technique is currently forbidden as...