Analogies or metaphors are often useful for starting to understand a given topic, but in my view, serious engagement requires that we progress from this to a description of what is really going on operationally. (Technically, at some linguistic level, I’m sure it all remains some kind of metaphor, but at least things get much, much more concrete.)
The blog Gene Expression has a recent post which explains why when we read a headline about a “gene for depression” or whatever, this is usually very misleading. It is a model of science writing. It’s not easy to engage seriously with the science, avoid jargon, and keep your eye on the main issue. I think that a broadly educated person in the 21st century should have the level of understanding on this topic that you will get from the post.
I wrote an article for National Review a couple of years ago in which I argued that the fact of our ignorance in this area — that while intelligence and other mental traits have been understood to be somewhat heritable since at least the time of Homer, we do not have the practical ability to understand why person X has normal psychological make-up Y based on analysis of his or her genome — is likely to be very important to thinking about public policy in the upcoming decades.