The whole secret of genetics is exactly like the secret of the economic free market.

No one KNOWS what the "best" genes are, just like no one knows what the "best" cars or soaps are. What might be considered a genetic "mistake" can in some cases be an asset under certain environments. Attempting wide scale control of the process of evolution leads to problems. A wide genetic diversity is an organism's best defense against whatever the environment might throw at it.

So, while a case might be made for eliminating an obvious genetic flaw like one for a certain disease, one has to be extremely careful, and might I say, humble about this procedure. The more we know about the genetic code, the more we realize we don't know about how things are intertwined. Although I support research in genetic engineering, wide scale application of the process, i.e. applying it to a large population, is a potential mine field.

I had this argument once with someone who proposed that if we found a "gene" for homosexuality, that it should be eliminated. I disagreed. Aside from the obvious problems of how one would "eliminate" such a gene without eliminating individual rights, I pointed out that a "gene" for homosexuality should, by definition, have already weeded itself out of the species. The fact that something that so obviously works against reproduction is still in the gene pool after millennia, implied to me that if such a gene actually existed, it must be tied to something unrelated to sexuality yet extremely beneficial. It's just common sense. What it might be, I wouldn't know, but if we ever found it, I would think a lot more than twice before trying to eliminate it.