_throwaway1843

I think there should be a ban on "owning" custom sequences of DNA, as it will eventually lead to an accumulation of most of our "biological capital" in the hands of very few companies, which could then effectively control what and how we eat (and many other things as well). Already now most biodiversity has vanished from agriculture, with only a handful of different crop species accounting for more than 99 % of all harvests. This is highly dangerous economically, politically and environmentally.

Yes very good point, I didn't want to mention Monsanto but I also think they're probably the company that is most likely to use such a technology on animals in the future, if they might get the chance to do so.

Star Trek depicted one of the scarier applications of such a technology: There, The Jem'Hadaar are a genetically engineered race of warriors controlled by the Dominion, who exert power over them by being the sole provider of a substance (Ketracel-White) that they need in order to survive:

https://en.wikipedia.org/wiki/Dominion_(Star_Trek) http://memory-alpha.wikia.com/wiki/Ketracel-white

If my reading of the paper is correct, the unnatural XY base pair doesn't have any function per se, but without it the organism fails to replicate its DNA and quickly dies. Hence you can argue that after introducing it, the XY base pair has a vital function, as without it the organism can't survive anymore. And since the organism has no way to synthesize X & Y itself, it needs to be supplied from the outside for its whole lifetime. This, in turn, provides a neat way to build "self-terminating" organisms that depend on a steady supplement of the given substance. One could of course argue that vitamins are exactly the same, but contrary to those the artificial base pairs would not be found in the wild, so supply could be controlled more easily.