Murky Thoughts brings up a good point in the discussion about nature vs nurture as factors in personal responsibility for behavior... that genes != nature... all that is nature is not necessarily hardwired in the genes. Well, yes and no.
The frontal lobe development that occurs in adolescence and early adulthood IS directed by genes, but is also influenced by environment, some of which is by choice (marijuana, stress of half-time job while attending college, headbutting soccer balls) and some of it is not (lead in the drinking water, malnutrition due to family's poverty, head injury from accidental fall down steps).
To complicate matters, just because you have the gene(s) for, say, alcoholism, doesn't mean you will become alcoholic. If you never pick up a drink, you won't become alcoholic. Ahh, but what if you knew you have the alcoholism gene, and you knowingly drank alcohol and placed yourself at higher risk of becoming alcoholic? How is that choice viewed by society, compared with the choice of taking that first drink while not knowing of the risk?
I think it comes down to intent and risk tolerance. Do you intend to become addicted to alcohol? If so, that's either stupid or pathetic. Perhaps you are a gambler. You may decide to take a 30% risk of becoming alcoholic by taking that first drink, while others may find that a 5% risk is too high to accept.
Here's where knowing more about our defining genes, and about how they interact with environment, should increase, not decrease, our responsibility. The dystopic geneticomedicolegal future may have been foreshadowed in The Minority Report, where people are arrested before they commit the crime. It is easy to imagine being fined or taxed a higher amount if we choose lifestyles which interact with our personal genetic knowledge in a manner which increases the costs to society. We see this now with increased insurance premiums for smokers. Why not drinkers? Or, more specifically, why not folks with alcoholism genes who drink anyway... but no tax for gene-free folks who drink. Scorn the guy who knows he has the Vioxx-causes-heart-attack gene but takes it anyway due to pain, while giving a heartfelt pat on the back to the guy who inexplicably suffers the same fate. Sounds like a Kurt Vonnegut story.
I'd like to imagine a world where we can choose to learn about our genes which define our propensity to develop alcoholism, to be creative, or to develop stomach cancer... and then use that information to help make more informed decisions about where to focus our resources, take risks, avoid genetic traps.
Mind you, this does not mean that people will choose to be limited by what their G, C, A, & T-leaves tell them. Some will choose to accept our current concept of what a collection of genes mean, while others with a more oppositional bent will choose to damn the torpedoes and full speed ahead into genetically uncharted territories, in the same way that some amputees will run a marathon.
Just some food for thought.