Siddhartha Mukherjee won a Pulitzer Prize in 2011 for his book “The Emperor of All Maladies: A Biography of Cancer.” This hour, he’ll take us from Gregor Mendel’s 19th Century experiments with pea plants to current methods of gene editing with CRISPR/Cas9. He writes about it all in his latest effort, “The Gene: An Intimate History” (Scribner).