It took another fifteen years before scientists began to deliver engineered DNA into the cells of humans. The goal was similar to creating a drug. There was no attempt to change the DNA of the patient; it was not gene editing. Instead, gene therapy involved delivering into the patient’s cells some DNA that had been engineered to counteract the faulty gene that caused the disease. The first trial came in 1990 on a four-year-old girl with a genetic mutation that crippled her immune system and left her at risk for infection. Doctors found a way to get functioning copies of the missing gene into
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