British fertility specialists have developed a powerful new way to test embryos for inherited diseases, offering hundreds of couples their first realistic chance of having healthy children. The procedure has been hailed as a big advance, boosting the number of diseases clinics can test for from about 200 to nearly 6,000. It will allow doctors to test for the first time a vast array of inherited diseases for which the specific genetic mutation is not known, such as Duchenne's muscular dystrophy (DMD) and some forms of cystic fibrosis. Using the technique, doctors can examine every embryo created for a couple...