The story of the gene begins in earnest in an obscure Augustinian abbey in Moravia in 1856 where Gregor Mendel, a monk working with pea plants, stumbles on the idea of a "unit of heredity." It intersects with Darwin's theory of evolution, and collides with the horrors of Nazi eugenics in the 1940s. The gene transforms postwar biology. It invades discourses concerning race and identity and provides startling answers to some of the most potent questions coursing through our political and cultural realms. It reorganizes our understanding of sexuality, gender identity, sexual orientation, temperament, choice, and free will, thus raising the most urgent questions affecting our personal realms. Above all, the story of the gene is driven by human ingenuity and obsessive minds -- from Mendel and Darwin to Francis Crick, James Watson, and Rosalind Franklin to the thousands of scientists working today to understand the code of codes. Woven through the book is the story of author Mukherjee's own family and its recurring pattern of schizophrenia, a haunting reminder that the science of genetics is not confined to the laboratory but is vitally relevant to everyday lives. The moral complexity of genetics reverberates even more urgently today as we learn to "read" and "write" the human genome -- unleashing the potential to change the fates and identities of our children and our children's children.