Gene therapies emerged--appropriately--about the same time the first human genome was being mapped during the 1990s, though the study of gene therapies goes back as far as the 1970s. They work by actually tampering with a person’s DNA--usually by encoding a functioning gene to replace a mutated one, or by introducing DNA that encodes a therapeutic protein into the body. Clinical trials have gone on for years. Early on, failures caused many to dismiss the idea of tampering with genes. But later--in the following decade--many in the medical community changed their minds after witnessing a series of successes. Among them: China, which approved its first gene therapy in 2003.