Expert systems are not intelligent. They're nothing more than a fancy version of Animals. If/then/else isn't even weak AI and a binary search of an index is just a search. It doesn't mimic an expert, because experts only start with simple diagnostic tools like that. That's the beginning, not the end. Experts know when answers are off and know how to recover from it - when it's unimportant and when it's absolutely critical. Experts also know how to handle cases never encountered before, because they don't just know a bunch of checklist questions, they know how information relates and they know the patterns that are generic across all cases, known and unknown. You can't program an Expert System Shell with Category Theory maps, Prolog isn't going to know what to do with meta-abstraction.
Neural Networks are debatable. Fundamentally, a Neural Network is a very large set of multi-input gates. Nothing more. If it's trained, then all you've done is simplified the derivation of the gates. You've not added any intelligence. Self-organizing networks are another beast entirely. These can be argued to be "intelligent", since the human brain is ultimately nothing more than a gigantic conglomerate of gates itself. The only reason you have the illusion of intelligence is that there's self-organizing involved. However, no self-organizing neural net on any computer yet built is so powerful that it can simulate the functioning of a nematode's brain. Strong AI, which is what most non-CS people think of as AI, cannot yet even be described. We have no comprehension of what it is, therefore cannot build it.
What the professor is really talking about though, as indicated by the reference to cellular biology, is not AI but ALife. Nothing currently in existence can be called true artificial life, although the Bugs program from Scientific American is a good start. Artificial Life is many orders of magnitude harder than Strong AI. It's not enough to emulate the properties of intelligence, you have to emulate the reason for there needing to be intelligence in the first place. Even those working on Strong AI aren't tackling such self-consistency issues, far too complex for them.
(It's clear that most AI work is incompatible with a self-consistent Strong AI, so I'm inclined to believe Singularity isn't going to be here for a while. Progress is, as others have noted, somewhere between non-linear and exponential, but even if we assume exponential, it'll be between 75-150 years before Strong Artificial Life is within reach, where Strong ALife is Strong AI and Artificial Life and self-consistency.)