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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!

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It's not adviseable as a resource, but I suggest you look into Ender's Shadow (specificly pages 131-138) that has some information on the possibilities of the human genome. Again, not advisable as a source of knowledge, but the points made in those pages are worth looking into. Sorry if its not useful. –  user5058 Dec 2 '13 at 1:47
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First of all it is important to note that, within certain limits, human DNA is not much different than, say, a mouse DNA: it has the same structure, it is constituted by the same bases etc etc. Therefore it is teorethically possible (leaving aside ethical issues, of course) to selectively modify it as you would do for a mouse. There are, however, some technical issues and obviously many ethical ones.

To answer specifically to your questions

Is it even theoretically possible to alter human genetics using only an injected substance?

Yes it is. Aside from the good example of radioactive substances given by Alexander, another good one (and probably one that is more common) is that of chemical mutagens.

It is important to understand that the mutation caused by these substances are random, or only partially selective. For instance, certain substances, called intercalating agents can interpose themselves in between the bases of the DNA, interfering and possibly giving rise to mutations during DNA replication.

Other substances such as alkilating agents are a bit more specific, although still not gene- or locus- specific. For instance ethylnitrosourea (ENU) favours A->T base transversions and AT->GC transitions.

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.

The immune system would not necessarily kill cells with mutations. Think of what happens during cancer developement. Also, an extremely important point: mutating a somatic cell (i.e. not a sperm or an egg) can induce a mutant phenotype in the individual but it will not be transmitted to his/her progeny.

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?

As Alexander says, there is much research in this field. Some attempts of gene therapy have indeed been made, and some have a big potential. We are, however, still far away for gene therapy to become a routine treatment.

Also, remember that:

  1. not all diseases are genetic diseases
  2. not all genetic diseases are monogenic: some derive from a complex interplay of different factors and hence curing them is not as simple as providing the correct version of the mutated gene.

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?

Yes, but I would say that we are very very far away from a complete understanding of how thought and emotions are coded in our brain. The very difficult point is that one needs to study these events at multiple scales. We can study a big region of the brain and say that it is involved in fear coding, for instance. But then if you want to go deeper and study what happens at the single cell level you need to look at a lot of different cells to see how they interact between each other. From the other side of the "size scale", it is possible to study biochemical processes in the single neuron, but then again it is difficult to study how these processes are integrated in big networks of cells, especially in vivo.

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Thank you very much for the detailed answer. I'll certainly have to read into behavioral genetics! –  Polynomial Apr 12 '12 at 18:50
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Concerning the first question, it is very well possible to alter human genetics by injecting a highly radio-active substance that will eventually cause mutations almost all cells. The lifespan will be dramatically reduced, however and the condition is known as "radiation sickness"(link to Wikipedia).

But the person probably means so-called "directed mutations" (link to Wikipedia), when the changes of genetic information is not random, but rather at a certain place and towards a certain function.

Second point, this is the area of extensive research: if we could specifically cure a gene than many diseases that are incurable now (like cystic fibrosis) could be effectively treated. The complete nanotechnology (link to Wikipedia) is all about it.

As to the third point, this is also a very old discussion about the role of nature (=genetics) and nurture (environment). Answering this question in the scope of other questions I can suggest that (genetic) knocking-out some inhibiting receptor systems in brain can lead to certain malfunctions and deceases, including the lymbic system that is responsible for emotions and perception.

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Thanks for the answer. I hadn't considered nanotechnology as a possible injection payload - certainly very interesting stuff! I'll read through those wiki articles for more information. –  Polynomial Apr 12 '12 at 18:51
    
Small point; if you're thinking about genome-altering nanotech, perhaps you're thinking of one of many viruses. –  Ryan Aug 9 '13 at 21:22
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