Readers may recall that a couple of days ago, we noted the surprising find that even more species of bacteria do not use the traditional universal genetic code they were thought to have inherited from the First Cell or whatever. From a researcher: “Changing the genetic code requires changing ancient, important molecules like tRNAs that are so fundamental to how biology works.”
Tim Standish at the Geoscience Research Institute offers some thoughts on the situation — and the spin put on it:
The spin inherent in the headline for this article is fascinating: Screen of 250,000 Species Reveals Tweaks to Genetic Code.
Changing codon meaning isn’t merely a tweak. As one of the authors notes, “It’s just mind-boggling that an organism could survive that.” But he is dead wrong when he says, “Stop codon shifts are considerably less ‘dramatic’”. Changing a stop codon seems significantly more challenging than changing any other codon meaning because the mechanism for stop codon recognition is totally different and involves more than RNA-RNA interactions.
It’s also a mindbender that on average having 1/3 of genes read through after a regular stop codon, producing who knows what random AA sequence until another still functioning stop codon is encountered, could be survived. Even if either kind of change was survivable, the idea that there might be some incremental increase in fitness at each necessary step along the way makes about as much sense as hitting one’s big toe with a hammer and expecting this will make you a faster runner.
As is so common with these things, some functional explanation for why the different genetic codes in these new examples are somehow better than the “universal” code is treated as sufficient to explain these impossible changes that must be achieved in an incremental and unguided way. This implies that some need on the part of an organism is miraculously capable of producing an outcome that resolves the need. If only life was really like that, because I need a few million dollars to buy a home on the shore of Sydney Harbour and a private jet to get there.
I’m not sure that they are listing all known genetic codes in this article as there are variations in the genetic codes used in mitochondria, and these show an interesting pattern of distribution that requires the same changes in multiple taxa. In addition, using a different genetic code than the nucleus makes moving genes from mtDNA to chromosomal DNA and expecting a good outcome incredibly optimistic.
Good luck with the private jet and Sydney Harbour, Tim. That mind of magic only works with Darwinian theory. Not with life.
You may also wish to read: Five more species of bacteria use alternate genetic codes At The Scientist: “The genetic code has been set in stone for 3 billion years,” study coauthor Yekaterina Shulgina, a Harvard University graduate student in systems biology, tells The Scientist. “The fact that some organisms have found a way to change it is really fascinating to me. Changing the genetic code requires changing ancient, important molecules like tRNAs that are so fundamental to how biology works.”