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Default Where's your god now?

08-05-14, 22:28 #1
First living thing with ‘alien’ DNA created in the lab: We are now officially playing God


Scientists have succeeded in creating the first organism with “alien” DNA. In normal DNA, which can be found within the genes of every organism , the twin strands of the double helix are bonded together with four bases, known as T, G, A, and C. In this new organism, the researchers added two new bases, X and Y, creating a new form of DNA that (as far as we know) has never occurred after billions of years of evolution on Earth or elsewhere in the universe. Remarkably, the semi-synthetic alien organism continued to reproduce normally, preserving the new alien DNA during reproduction. In the future, this breakthrough should allow for the creation of highly customized organisms — bacteria, animals, humans — that behave in weird and wonderful ways that mundane four-base DNA would never allow.

DNA TattooThis landmark study, 15 years in the making, was carried out by scientists at the Scripps Research Institute and published in Nature today [doi:10.1038/nature13314 - "A semi-synthetic organism with an expanded genetic alphabet"]. In normal DNA, two separate strands are entwined in a double helix. These strands are connected together via four different bases, adenine (A), thymine (T), cytosine (C), and guanine (G). A always bonds with T, and C always bonds with G, creating a fairly simple “language” of base pairs — ATCGAAATGCC, etc. Combine a few dozen base pairs together in a long strand of DNA and you then have a gene, which tells the organism how to produce a certain protein. If you know the sequence of letters down one strand of the helix, you always know what other letter is. This “complementarity” is the fundamental reason why a DNA helix can be split down the middle, and then have the other half perfectly recreated. There, I just explained in about 150 words two of the most vital processes to all life that we know of.

In this new study, the Scripps scientists found a method of inserting a new base pair into the DNA of an e. coli bacterium. These two new bases are represented by the letters X and Y, but the actual chemicals are the rather cryptic “d5SICS” and “dNaM.” A previous in vitro (test tube) study had shown that these two chemicals were compatible with the enzymes that split and copy DNA. “We didn’t even think back then that we could move into an organism with this base pair,” said Denis Malyshev, first author of the paper. Fortunately, he was wrong.

The full Nature write-up is worth reading if you want the nitty-gritty details, but here’s the short version. First, the scientists genetically engineered an e. coli bacterium to allow the new chemicals (d5SICS and dNaM) through the cell membrane. Then they inserted a DNA plasmid (a small loop of DNA) that contained a single XY base pair into the bacterium. As long as the new chemicals were available, the bacterium continued to reproduce normally, copying and passing on the new DNA, alien plasmid and all. In the study, this process seems to have carried on flawlessly for almost a week.
Synthetic DNA, with a new XY base pair

Synthetic DNA, with a new XY base pair

For now, the XY base pair does nothing; it just sits there in the DNA, waiting to be copied. In this form, it could be used as biological data storage — which, as we’ve covered previously, could result in hundreds of terabytes of data being stored in a single gram of synthetic, alien DNA. Floyd Romesberg, who led the research, has much grander plans. “If you read a book that was written with four letters, you’re not going to be able to tell many interesting stories,” Romesberg says. “If you’re given more letters, you can invent new words, you can find new ways to use those words and you can probably tell more interesting stories.”

DNA headerNow his target is to find a way of getting the alien DNA to actually do something, such as producing amino acids (and thus proteins) that aren’t found in nature. If Romesberg and co. can crack that nut, then it will suddenly become possible to engineer cells that produce proteins that target cancer cells, or special amino acids that help with fluorescent microscopy, or new drugs/gene therapies that do weird and wonderful things. (Read: What is transhumanism, or, what does it mean to be human?)

Ultimately it may even be possible to create a wholly synthetic organism with DNA that contains dozens (or hundreds) of different base pairs that can produce an almost infinitely complex library of amino acids and proteins. At that point, we’d basically be rewriting some four billion years of evolution. The organisms and creatures that would arise would be unrecognizable, and be capable of… well, just about anything that a white-coat wearing maniac can dream up.


http://www.extremetech.com/extreme/1...ly-playing-god

só colocar num pouco de água, chacoalhar por uns 5 milhões de anos e esperar a mágica?





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08-05-14, 22:35 #2
aparentemente não

http://www.nature.com/nature/journal...ture13314.html


Organisms are defined by the information encoded in their genomes, and since the origin of life this information has been encoded using a two-base-pair genetic alphabet (A–T and G–C). In vitro, the alphabet has been expanded to include several unnatural base pairs (UBPs)1, 2, 3. We have developed a class of UBPs formed between nucleotides bearing hydrophobic nucleobases, exemplified by the pair formed between d5SICS and dNaM (d5SICS–dNaM), which is efficiently PCR-amplified1 and transcribed4, 5 in vitro, and whose unique mechanism of replication has been characterized6, 7. However, expansion of an organism’s genetic alphabet presents new and unprecedented challenges: the unnatural nucleoside triphosphates must be available inside the cell; endogenous polymerases must be able to use the unnatural triphosphates to faithfully replicate DNA containing the UBP within the complex cellular milieu; and finally, the UBP must be stable in the presence of pathways that maintain the integrity of DNA. Here we show that an exogenously expressed algal nucleotide triphosphate transporter efficiently imports the triphosphates of both d5SICS and dNaM (d5SICSTP and dNaMTP) into Escherichia coli, and that the endogenous replication machinery uses them to accurately replicate a plasmid containing d5SICS–dNaM. Neither the presence of the unnatural triphosphates nor the replication of the UBP introduces a notable growth burden. Lastly, we find that the UBP is not efficiently excised by DNA repair pathways. Thus, the resulting bacterium is the first organism to propagate stably an expanded genetic alphabet.

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