Several steps back

Just before falling asleep last night I realized that I should take several steps back and explain some biology basics before jumping into my frustrations with microarrays. Although no one may ever read this, if some non-biology major comes along, I would like her/him to understand what I'm talking to about. In general I feel science needs to be more accessible to the general public, and I don't think I'm helping if I just start blabbering jargon.

So, I have decided that before continuing with my microarray story, I'm going to write several posts as a post-introduction to the topic.