A great book on the general context of what counts as an explanation in biology -- and, by extension, why the mathematical biological approach advanced by Turing never really caught on -- is presented in Evelyn Fox Keller's Making Sense of Life: Explaining Biological Development with Models, Metaphors, and Machines (Harvard U.P., 2003). A short version of the argument is presented in this article from Project Syndicate: http://www.project-syndicate.org/commentary/biology-s-clash-...