I believe I have commented here previously about CRISPR, which is a recently developed method for precise editing of genes borrowed from prokaryotic cells. (If you aren't up to speed on the technical background, that's not really the point of this post. But I will be kind enough to say that prokaryotes are bacteria and archaea, single celled organisms without a nucleus. We are eukaryotes.) It enables scientists to make specific changes at exact sites in a gene, not without some rate of error although they are continually improving the technique.
You don't have to think very hard to see where this could lead. Although we don't yet know enough about the genetic basis of human traits such as intelligence or ability to play basketball, while we're figuring that out we could correct genetic diseases caused by single mutations. If you edit genes in a zygote, the changes will end up in all the cells of the resulting embryo, and so be heritable by the genetically enhanced persons offspring. Yep, super
So, this being problematic for many people it is not currently allowed in the U.S. Now the UK has given permission for a single scientist to edit genes in human embryos within 7 days of fertilization, just to check out the methods. Then she is required to discard the embryos.
As you might imagine, I don't have a problem with this. These are surplus embryos from in vitro fertilization, of which thousands are routinely discarded anyway. The anti-abortionists for the most part don't seem to have a problem with that, oddly, even though according to their ideology these are morally indistinguishable from babies. But I expect this will get their attention, not because it's any different by any rationally defensible criteria but because it creates an intuitive offense to moral sensibility, i.e. the embryos are a means to an end.
Since they aren't people, that shouldn't matter. But if you think they are, it must, no?
What will probably trouble many more people is not these particular experiments, but where we might end up in the future. If it's possible to create genetically enhanced humans, it's hard to see how it will never happen.