[vbuwivbiu]

the point isn't about actually growing an adult fluorescent horse, it's about proving the principle in an embryo - which takes days. It's already been done with mice, but I agree it's a simple example.

Your point about multiple genes is a very good one but we have a good understanding of how some gene networks work already and the rest will follow.

[Laforet]

The problem with embyros is that they can be inject with any DNA for a trasient positive result but these may well be discarded or inactivated during development. The recently debuked STAP cells used injected embyros as evidence and it turned out to be either a fluke or outright fraud. To prove the concept you really need a stable F1 generation to illustrate that the trait can be passed down in the germline.

I'd say that our ability to interact with the genome is still rather crude, else we'd have already cured cancer by now - we already have a pretty good understanding of the cellular biology of cancer but it only helps us so much.