Scientists are making DNA that uses letters other than AGCT

July 23, 2001 6:21 PM

Scientists are making DNA that uses letters other than AGCT
Underlying the chemicals is a code. DNA is composed of pairs of four types of proteins. This project at Scripps Research Institute is attempting to design a DNA which uses different proteins to convey genetic information. The ultimate goal would be to have a functioning organism with a genetic code that uses a different "alphabet" to "communicate" the same "message" You know what this means? If they can get it to work, language wins! The world will truly be proven to be a "discursive" formation. (The language metaphor comes courtesy of the NYT, but I believe it is more than apt.)
posted by rschram (16 comments total)

quantum genetics?
posted by machaus at 7:11 PM on July 23, 2001

Just to be pedantic: they're not changing DNA; they're still going to be using adenine, guanine, cytosine and thymine.

What they're doing is to alter the transfer RNA used to decode RNA codons into amino acids, so as to use chemicals in that family which are not now used. The twenty amino acids currently used by life are not the only chemicals available which could be used.

It's an interesting exercise but I'm not really sure what they expect to accomplish, really.

By the way, the article is wrong about something: there are three entries out of 64 which don't encode an amino acid, but they're not "nonsense". They are "stop" signals and indicate that the protein has come to an end. The other 61 all encode an amino acid.
posted by Steven Den Beste at 7:24 PM on July 23, 2001

The NYT link (above) talks about adding artificial bases to the DNA itself. This is discussed as a way to get around using the stop signals to code for other amino acids.
posted by lagado at 8:23 PM on July 23, 2001

Artificial base pairs are being developed, and could make genetic engineering a bit safer to the natural world.
posted by skyline at 8:52 PM on July 23, 2001

That link was greek to me.
posted by lagado at 9:45 PM on July 23, 2001

heh...had it been in English, I might still have found it indecipherable...

so I'm brazenly asking for a free Cliff-notes tutorial - why would using artificial base pairs make genetic engineering safer?

Or am I gonna hafta Google all to hell and gone?
posted by Opus Dark at 9:57 PM on July 23, 2001

Critters using artificial base pairs would not be able to reproduce without special nutrients. If they escaped, they'd die without spreading.
posted by Steven Den Beste at 10:31 PM on July 23, 2001

Critters using artificial base pairs would not be able to reproduce without special nutrients. If they escaped, they'd die without spreading.

Jurassic park anyone? :)
posted by riffola at 10:34 PM on July 23, 2001

Omigod they're making life! do they think they're god or something?! we have to stop them. or they'll do an experiment and it'll spill and get outta controal and turn into a mutant alien!! its like in that movie, i forget the name.
posted by jrbender at 10:39 PM on July 23, 2001

I think that's 'Every movie about genetic engineering ever made except for Gattaca', jrbender.
posted by darukaru at 3:00 AM on July 24, 2001

Steven, the term "nonsense" is a bit of molecular biological jargon for a stop codon. I'm not sure of its etymology, but I believe it arose in contrast to a "missense" mutation, i.e. a DNA base pair change resulting in a different amino acid in the translated protein. A "nonsense" mutation, by contrast, is a DNA base pair change to a (premature) stop codon. Whereas a "missense" mutation usually results in diminished functionality, a typical "nonsense" mutation eliminates it entirely.
posted by whuppy at 6:41 AM on July 24, 2001

Ok, regarding the language metaphor -- I didn't pick up on this from the link, but rschram's summary made me think of it this way -- would it establish that the true defining feature of life would be the information encoded into the bases/amino acids/etc. rather than the chemicals themselves? Now that's a breakthrough I'd like to see. (For one thing, it would legitimize and expand artificial intelligence/philosophy of consciousness enormously.)
posted by tweebiscuit at 6:44 AM on July 24, 2001

This is very cool research, by the way. The genetic code of DNA is linked to the expression of protein via transfer RNA (tRNA), which is a complex structure that has an amino acid at one end and an "anticodon" at the other end. The system by which tRNAs are synthesized, in which the correct anticodon is matched with the correct amino acid, is currently poorly understood and has been termed "the second genetic code". The ability to engineer tRNAs with novel amino acids will enable the construction of proteins with functions hitherto unfathomable. This is one of those technologies whose effects might reverberate far into the future. My guess is nanotechnology -- you create a bunch of amino acids that function as logical units in a finite state machine and string 'em together. And then you expose the critters to mutagens and screen 'em for how well they solve a problem: genetic algorithm!
posted by whuppy at 6:53 AM on July 24, 2001

Oh, and PS: Anybody interested in the language metaphor should read and re-read Godel, Escher, Bach.
posted by whuppy at 6:57 AM on July 24, 2001

PPS: lagado, what the article says is that both research teams are rejiggering tRNAs to accept "unnatural" amino acids. This has nothing to do with changing the bases used in nucleic acids. IOW, the DNA and RNA use the same letters, but the researchers are trying to change the meaning of a couple of the words.
PPPS: The article did give a misleading impression about "nonsense" codons.
posted by whuppy at 7:07 AM on July 24, 2001

Interesting posts, whuppy. I was just referring to this passage in the New York Times article which wasn't talking specifically about Scripps research paper.

So if scientists want to introduce many new amino acids, new codons will be needed. That is why they are trying to add letters to the genetic alphabet. If DNA consisted of six bases - say, A, C, G, T, X and Y - there could be 216 codons instead of 64.

Such artificial DNA bases have been made by Dr. Benner in Florida, Dr. Romesburg at Scripps and Dr. Eric T. Kool, a chemistry professor at Stanford. Besides fitting into the double helix of DNA, each artificial base must pair with only one artificial counterpart, just as A always pairs with T, and C with G. Such pairing is essential for accurate DNA replication.
posted by lagado at 7:45 AM on July 24, 2001