This area is called gene therapy. It's being experimented with in Canada, at a clinical level, for a specific gene, for a one-at-a-time kind of thing. Changing everybody's code at a more multi-genetic level will be hugely challenging. We're not there, but for certain diseases of the eye, for example, there are clinical trials ongoing in Canada. Dogs have been cured of blindness through this gene therapy.
On March 5th, 2013. See this statement in context.