Mukherjee writes well and engagingly about a number of stories involving the development of genetics and its impact. However, I do not quite trust him as a historian of ideas; his accounts of some developments are a bit too neat. His account of gene regulation and epigenetics is flawed. He seems to believe that regulation by transcription factors is transient only, and so does not explain why cells become "locked into" their respective developmental fates. This is wrong. Epigenetics, i.e. DNA methylation and histone modification, is not nearly as essential as Mukherjee makes it out to be. He brings out some important ethical issues, but does not have a very well organized approach, so the discussion leaves the reader hanging. The 3 stars are 3+.