Generally, patients have to show symptoms of a disease before they’re treated for it. But, increasingly, thanks to advances in precision medicine, some new treatments are focused on the prevention of diseases that people are most at risk for - and that risk is determined by their unique genetic data. While personalized medicine sounds great in principle, there are several challenges, including the cost. Antonio Regalado, senior editor of biomedicine for MIT Technology Review, and Carlos Bustamante, professor of biomedical data science, genetics, and biology at Stanford, talk to us about the past, present, and future of genetic data in health care.