Monday, the writer and oncologist Siddhartha Mukherjee is our guest. He’s written a new book that tells the epic tale of our quest to unravel the human genome. It’s the story of a long lineage of scientists—from Mendel, to Darwin, Watson, Crick, and countless others—and their efforts to understand the workings of the very threads of our existence. But how, Mukherjee wonders, can we best apply that knowledge? And what does it mean to be human when we can read and write our own genetic information?