So you decide to jump into this thread a week after it's dead huh? Remind me, what's your job? You work in a biochemistry lab?

To summarize:
- Screening is easiest (aka not GM), modification is harder
- At conception is easiest, after is plausible but more work needed
- Things that are expensive get cheaper over time usually
- In the future many things may be different

So what's the current state of things? What could we feasibly do right now? We can obviously screen for many things, anything that has an associated gene identified can be screened - so the "Gattaca" scenario is already possible - yet strangely the world hasn't collapsed into dystopia. Perhaps it's not such a big deal afterall.

Been fairly busy lately so I haven't had the time to collect my thoughts and do the reading into the subject that I wanted until now. Yeah, I worked in a biochem lab for a couple of years, at present I'm just a tech at a hospital while waiting on medical school applications and such, though obviously I still try to keep up with research developments because it's interesting.

Gene therapy is essentially the current cutting edge of genetic modification. Contrary to what I was saying about pre-birth GM being easier than post, gene therapy is pretty much exclusively somatic (that is, done to the non sex-cells of the patient, which means that any modifications will not be passed on to their children). That said, there's a bevy of issues with our current methods: the (typically viral) vectors used for gene insertion carry risks (cancer, immune response, difficulty with insertion of longer sequences, etc.), current methods are typically not permanent and therefore require multiple sessions of therapy (which thereby adds the chance of the patient developing resistance to the method), we aren't currently really able to deal with conditions involving the contribution of multiple genes (e.g. Alzheimers, diabetes) and so on and so forth. I can elaborate on the reasons for these issues if you'd like but it gets fairly technical fairly quickly. Simplistically I think we can say that current methods can accomplish a lot of interesting things but they're fairly limited because they tend to involve insertion of a gene rather than direct modification of the genome - That is to say, our current way of doing things is to simply "drown out" the effects of an undesired mutation by introducing the "normal" version of the gene elsewhere and hoping its expression will compensate for the effects of the mutated one, rather than going in and editing the mutated gene so that it does what we want it to do (which seems much simpler in theory but is much more difficult to accomplish in practice).

I don't really think there is much discussion to be had about gene therapy, other than perhaps a potential to change hormone production, I can't help but see it as just a cure to genetic disorders. This sort of thing is obviously interesting and important but I doubt many people could argue against it. Therefore stem cell modification before birth seems to me to be much easier to have a 2 sided debate about because of the greater effect such changes would have on the patient as well as the ethical issues of whether parents should really be able to decide this sort of thing for their child. If a grown ass man wants his adrenal glands to be more active and we have the means to do this through genetic modification then good for him if he can afford it, if a parent wants the kid to be albino or something this is another matter since the kid doesn't have a say.

I know this sort of dilemma is common for all medical treatment of children who can't express consent or be trusted to choose for themselves, but when it is actually changing that child's genetic makeup I think it is a slightly more extreme issue.

In a lot of ways gene therapy is more important than pre-birth GM.

If we can get GT up to a level where it's viable, then any further advances in genetics can be applied to current generations. An albino kid could get their genes changed.

It would probably still take ages for the effect to be seen (new hair and skin cells need time to grow to replace the originals). I imagine that the main changes would be to do with hormone production, I imagine that with the current gym culture boom a lot of people would pay to have more testosterone in their blood being produced, I am sure it will eventually be possible to inject genes to make the body produce something akin to anabolic steroids at a steady rate. Physiological changes like height, skin or eye colour and neurophysiological stuff would probably require either a very long time or surgery to change, nevertheless, I am only speculating.