It’s a scenario that has haunted biologists since the dawn of the DNA age: the evil scientist custom-crafting a human being with test tubes and Petri dishes. So when a Chinese team revealed last month that it had used a new laboratory technique to alter a gene in human embryos, it set off an urgent debate over the ethics — and wisdom — of tinkering with the most basic building blocks of life. The technology makes genetic manipulations that were theoretical in the past seem easy to achieve — and soon. If scientists figure out how to do it in a way that’s safe for patients, gene editing could produce tremendously beneficial medical treatments. The Chinese researchers, for instance, were trying to repair a defect that causes beta thalassemia, a potentially fatal blood disorder. But a simple way to alter DNA could open the door to more frightening eugenic pursuits. That makes people nervous. 

“The positive side is, it allows regular biologists to change the DNA in any organism. The negative side is, it allows regular biologists to change the DNA in any organism,” said Harvard Medical School geneticist George Church. “You can twist any technology into something bad.” In the last few months, many researchers have come to realize that the new gene editing tool, known as CRISPR/Cas9, might provide an easy means for molding a person when he or she is just a single-celled embryo. FULL REPORT