In 1980 Mark Ptashne published a review entitled How λ repressor and Cro work followed by another, in 1988, called How eukaryotic transcriptional activators work. The bold — almost, some might feel, naïve — ambition these titles betray is unashamedly the author’s: to generate a coherent picture of how genes are switched on and off. Mark Ptashne’s approach has always been transparent. During gro...