Scientists at The Scripps Research Institute have created a bacterium with two extra synthetic base pairs, and it's "holding on" to them as it divides.
The implications of this are quite fascinating. There's no applications for this at all - but it's helped us learn something of how DNA works.
It's also proved in concept that DNA does not have to use the four base pairs our kind of life has settled on.
And it's proved in concept that DNA using multiple different kinds of base pairs could be combined to create a stable organism.
1. Life does not have to be based off of our base pairs.
2. Bacterium from an ecosystem based off of one set of base pairs could "take in" DNA from another. This means that cross-planetary disease/plague is possible. Viruses could even potentially do the same trick. Uh oh.
3. Hello, Mr. Spock. As in, it might be possible for a highly advanced civilization to genetically engineer stable, viable, healthy offspring from two (or more) sentient beings from different planets even if their DNA does not use the same base pairs...
In other words, fun for science fiction writers.