I recently had a conversation with a rather *unusual* gentleman who was, let's say, more than a little partial to conspiracy theories. He has this idea that governments are lowering "nanowires" from drones, to inject people with chemicals that modify their genetics in order to reduce their lifespan dramatically, or change their opinions and thoughts.

Clearly this man was a fruitcake, and the complexities of his psychology probably warrant a whole separate debate, but he did get me thinking about the theoretical side of how such a thing might be done.

So, as such, I have a few questions on the matter:

1. Is it even *theoretically possible* to alter human genetics using only an injected substance? I'd imagine trying to get a single DNA change to propogate through the entire body without being killed off by the immune system would be near impossible.
2. Since we are aware of genetic markers that are related to predispositions to certain medical conditions (e.g. heart problems, cancers, high blood pressure, strokes, etc), is it possible to modify human DNA to create these issues in a living person?
3. Has much research gone into how genetics affects thought and opinion, or the way we perceive and react to situations at an emotional level? If so, is it *theoretically* possible to alter this at a biological level?

I'm certainly not advocating any of this, and I apologise for the unusual nature of the question, but it's something I certainly find interesting to think about!