But the important question is, what does Hughes mean by "fundamental biology"? In his letter he makes it clear that he is talking about an award that recognizes all discoveries in biology and not just those related to medicine. But the problem is that several of the biological discoveries that were later recognized by the Nobel Prize in medicine had little to do with medicine when they were made. For instance what would you say about the discovery of telomerase (2009)? Or cell cycle control (2000)? Or any number of discoveries in molecular biology including restriction enzymes, DNA and RNA polymerase, phosphorylation or indeed, the structure of DNA itself? By any definition all of these discoveries seem to fall under the "fundamental biology" rubric and I think even Hughes would have a hard time denying this. It just happened that most of them also turned out to be important for medicine (and why not, medicine is after all grounded in biology).
Perhaps Hughes means discoveries in "non-molecular" biology including ecology, evolutionary biology. But I believe that these fields are often honored by the Crafoord Prize which has gone to thinkers like E O Wilson, Robert May and William Hamilton. Maybe the Crafoord doesn't quite satisfy biologists' Nobel cravings because only one prize is awarded every year to different fields. It's also sort of odd that the Nobel Prize in medicine was only once awarded to ethologists studying animal behavior, and perhaps they should hand out more of those. But in any case, I think there have been ample prizes awarded to fundamental biological discoveries, so it doesn't seem very meaningful to me to institute a separate prize for biology. And ultimately of course, there's not much point getting hung up over any of these prizes since the work done by these scientists speaks for itself.
But maybe having a separate biology prize would make chemists feel happier. Which may not be an entirely good thing.