Genes are not enough to explain the difference between a skin cell and a stem cell, a leaf cell and a root cell, or the complexity of the human brain. Genes don’t explain the subtle ways in which your parents’ environment before you were conceived might affect your offspring.
Another layer of complexity—the epigenome— is at work determining when and where genes are turned on and off.
Ryan Lister is unravelling this complexity. He’s created ways of mapping the millions of molecular markers of where genes have been switched on or off, has made the first maps of these markers in plants and humans, and has revealed key differences between the markers in cells with different fates.