Scientists have successfully edited the DNA of human embryos to erase a heritable heart condition that is known for causing sudden death in young competitive athletes, cracking open the doors to a controversial new era in medicine. This is the first time gene editing on human embryos has been conducted in the United States. Researchers said in interviews this week that they consider their work very basic. The embryos were allowed to grow for only a few days, and there was never any intention to implant them to create a pregnancy. But they also acknowledged that they will continue to move forward with the science, with the ultimate goal of being able to “correct” disease-causing genes in embryos that will develop into babies.