 Another important topic in the philosophy of molecular biology has been the concept of the gene (Beurton, Falk and Rheinberger 2000; Waters 2000, 2004; Griffiths and Stotz 2007). Philosophers have also written extensively on the concept of genetic information, the general tenor of the literature being that it is difficult to reconstruct this idea precisely in a way that does justice to the apparent weight placed on it by molecular biologists (Sarkar 1996; Maynard Smith 2000; Godfrey-Smith 2001; Griffiths 2001; Jablonka 2002; Rosenberg 2006). For example, does DNA actually carry semantic information (Shea 2007)? If it does not, is this a useful fiction, or is it hindering molecular biology (Levy 2001)? 