The kicker is there's no real way to easily tell what's what.

Too many people have gotten the notion that DNA is like lines of computer code, nice and orderly. A biological system is more of a matrix, with things affecting other things along unexpected lines and hidden connections. Human biology is an "operating system" that's been patched and re-patched by evolution since the dawn of life.

This is why I get nervous when people start talking about "engineering" these things at a fundamental level. I suspect that for a long time the science of genetic engineering will mostly consist of trial and error, with end results possibly generations into the future.

I'm not saying it should never be done, but a certain amount of humility and a huge amount of caution should be in the mix.