I was assuming that they were asking you to teach them to program, or at least give them a comprehensive survey of the field. What you said is the obvious short answer for people who are just asking to be polite or to get an idea of what you do.
Let's assume I have just said 'I do X for company Y'. Your next response might be along the lines of a) What languages/tools do you use?, b) What's a peptide?, c) Did you watch Daniel Hillis' Ted talk?, or d) I just published a phylogenetic pruning algorithm on arxiv, you should check it out.
Seems to me that there is a lot to be learned through conversation, even when neither party is doing any teaching.
