I'm going to get a Master's in Artificial Intelligence, likely a PhD in Molecular Biology afterwards. I'm thinking I can do computer vision as a hobby while putting most of my energy toward understanding the big picture of cellular processes, because computer vision is something I can performance check. That's why I'm leaning towards Molecular Biology over AI even though I'll have years of research experience in AI.
The problem is that I want to know too much. I want to study Cell Signaling/regulation, Genomics, Molecular Biology/Biochemistry/Structural Biology, and disease during my PhD to do some interdisciplinary research in all of it. I want to develop computational data mining models that can take entire cellular systems into account.
Is it unheard of to fully specialize in two subfields during a PhD and associate my research topic to cancer later on in my PhD over 5-7 years? Or must I, for example, study a single new enzyme in an important pathway across various environments only in biochemistry?
Can you have a more general PhD that is still a successful contribution to the field? Say an analysis that studies an entire biochemical pathway from genetics through molecular biology to cancer if I have two committee members (one in each subfield)?