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New Letters Added To the Genetic Alphabet
An anonymous reader writes with this excerpt from Quanta Magazine: [A]fter decades of work, [organic chemist Steven] Benner's team has synthesized artificially enhanced DNA that functions much like ordinary DNA, if not better. In two papers published in the Journal of the American Chemical Society last month, the researchers have shown that two synthetic nucleotides called P and Z fit seamlessly into DNA's helical structure, maintaining the natural shape of DNA. Moreover, DNA sequences incorporating these letters can evolve just like traditional DNA, a first for an expanded genetic alphabet.
In fact, the article continues, these new nucleotides can actually outperform their natural counterparts: "When challenged to evolve a segment that selectively binds to cancer cells, DNA sequences using P and Z did better than those without."
This is at least a bit over a year old.
Nature had a good publication on this a bit (same research group) over a year ago.
http://www.nature.com/news/fir...
For every problem, there is at least one solution that is simple, neat, and wrong.
Because nature is a slacker and it does the bare minimum when pushed until it's pushed again? That's how evolution works bro.
That's far, far away at this point. In cells, DNA is first "transcribed" to an RNA copy of the same information, then "translated" by building a protein based on that information. Neither of those steps will work correctly here. Transcription enzymes won't handle the new DNA letters, and there's no defined meaning for them in the standard translation code: at best they'll be misinterpreted as a different letter, and it's more likely that translation will simply fail. And unless you can make at least a handful of proteins, you can't make a virus.
The article I read also said "IT HAS 216 COMBINATIONS!!1!!@@!! REGULAR DNA ONLY HAS 20!!!@!". Which is stupid because they're counting two different ways. 6^3 is indeed 216, but 4^3 is 64, and 20 is 31% utilization of 64 possibilities.
The reason is that some combinations are reserved for start and stop codons, and most amino acids have 2 or 4 redundant codings. This both reduces the effect of random mutations, and also makes multi-frame coding work better by being less strict. The bits that match the codes to amino acids when building proteins probably use some kind of wildcards, reducing the number of them needed when you have to basically have a unique small chemical around to match each valid combination. It would be more realistic to say that the new base pairs would allow 45-50 or so new protein codings, still more than tripling the potential number of amino acids.
That being said, a new set of base pairs is really cool. There have been experiments to create alternate DNA codings by re-purposing some of the redundant codings, but there is a backward compatibility kind of problem when doing that. This not only allows a lot of new codes, but the new base pairs themselves have interesting properties. One even has a bond out to the side that you can connect things too. And the twisty folding stuff that RNA likes to do can become a lot more complicated.
And why does Earth life use only 4 base pairs? Probably because the extra complexity just isn't all that useful. CGAT has been around for a couple of billion years, so it's got more installed base behind it than QWERWTY vs DVORAK could ever have. Except this is more like adding a new row or three to QWERTY for more roman-letter characters, such as a bunch of letters with diacritical marks on them, like how the French went nuts romanizing Vietnamese.
#naabhaprzrag, #sverubfr-000, #agi-fcbafberq, negvpyr[pynff*=' negvpyr-ary-'] { qvfcynl: abar !vzcbegnag; }