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NASA - Astrobiology Basin Toplantisi


Sylian

Öne çıkan mesajlar

Ardeth said:

al işte demiştim beğenmedin di mi aliminyum folyolu canlılar çıkmadı diye

bu kadar önemli bir bulguyu taşak geçme diye yorumlamak resmen hırsından gözün dönmüş hehe


aliminyum folyo falan dalga geçiyorsun da..

diyelim 2miz de bir mağarada yaşıyoruz ve yiyecek kıtlığı çekiyoruz. Mağaranın çıkışını bir türlü bulamıyoruz, ve ben mağaranın çıkışında burger king olduğunu biliyorum, sen buna inanmıyorsun. Osman (nasa) geliyo ve dışarda ziyafet olduğunu ve mağara çıkışının nerde olduğunu bile bile, mağaranın bilmemne köşesinde bir bitki buldum kökleri yenilebiliomuş!!! diyo. Sen doğal olarak çok sevinip osmana tepki gösterenleri ayıplıyosun.

kreatif olasım geldi xD
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Ciddi eleştiriler de gelmiyor değil. Not exactly rocket science overhype diyerek bi de harvardlı bir mikrobioloji doktorunun görüşlerine link vermiş.

said:
But chemistry is much more predictable. Once DNA is out of the cell, pure chemical processes take over, and experiments have demonstrated that hydrolysis of arsenate links is fast. So you could do a simple experiment to test whether DNA had a phosphate or arsenate backbone: just remove DNA from the cell and put it in water for a few minutes. Then examine whether it hydrolyzes or not.

In an accidental way, Wolfe-Simon et al. performed precisely this experiment. The result indicates that the DNA of GFAJ-1 has a phosphate backbone.

The details are these: to isolate DNA, Wolfe-Simon et al. performed a phenol-chloroform extraction. In this technique, after cellular disruption, DNA and other cellular material were dissolved in water, and then the non-DNA material (such as lipids and proteins) were cleaned out of the mixture using phenol and chloroform. This is a pretty common laboratory procedure, and typically would take an hour or two. But here is the key point:

During this whole procedure, the DNA was in water.

Remember, proteins were removed from this mixture. Any cellular machinery that stabilized arsenate-DNA was removed. In the absence of biochemistry, pure chemistry takes over: any arsenate-DNA would have been quickly hydrolyzed in the water, breaking down into fragments of small size. Alternatively, phosphate-DNA would not hydrolyze quickly, and large-sized fragments might be recoverable.

So what size are the fragments of DNA extracted from GFAJ-1? They are large. Figure 1 shows a single strong band. This pattern is a bit unusual for a genomic DNA extract, but the important thing is that the fragments in this band have around 10,000 nucleotides between breaks in the DNA. These long chains of nucleotides did not hydrolyze in water. Yet it is precisely this DNA band that is claimed to have an arsenate backbone.


http://scienceblogs.com/webeasties/2010/12/guest_post_arsenate-based_dna.php?utm_medium=twitter&utm_source=twitterfeed
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