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DNA grows by two letters

Introversion

Introversion

Pie aren't squared, pie are round!
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Cue shark music? Isn't this the point in any schlock SF movie where something bursts out of someone's chest in a lab and skitters down the sewerways to grow and feed? :evil

New Letters Added to the Genetic Alphabet

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Now, after decades of work, 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.

The new nucleotides even 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.

“When you compare the four-nucleotide and six-nucleotide alphabet, the six-nucleotide version seems to have won out,” said Andrew Ellington, a biochemist at the University of Texas, Austin, who was not involved in the study.
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asroc

asroc

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That's definitely an impressive achievement, but I find it a little difficult to share the author's enthusiasm about the possible applications. The current system can already code for more than 20 (21) amino acids, but it doesn't because, as the author herself notes, it's too cumbersome and the error possibility is too high. Every day there are tens of thousands of naturally occurring instances of DNA damage already and it takes a host of enzymes to correct it and still produce the proper protein. Adding more bases into the mix is going to massively increase the maintenance needed, and it's fixing something that isn't broke. The possibility of more RNA enzymes is pretty interesting though.

And I really want to know what P and Z look like.
 
Roxxsmom

Roxxsmom

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The only benefit I can see from the point of view of such a system evolving naturally (given the number of amino acids we actually make) is increased redundancy in the genetic code, which could possibly make the system more forgiving of mutations (silent mutations are a possibility for some amino acid coding triplets but not others).

It is cool to see that different nucleotides can work in DNA, though. It makes one wonder which nucleotides might be used by alien life forms. Assuming, of course, that other life forms use nucleic acids for heredity at all.
 
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