MOSCOW, September 29 -. RIA Novosti Biologists from the US showed the likelihood of an alternative embodiment of the evolution of life, according to which the RNA and DNA molecules having simultaneously, bypassing the stage of the RNA world, according to a paper published in the journal Angewandte Chemie.
"Even if you believe in the" world of RNA, "you have to take on faith and the position that something existed simultaneously with the RNA and helped life evolve in the direction of DNA and proteins. Why not assume that DNA and RNA arose at the same time rather than trying to turn the second into the first with the help of some crazy chemistry "- said Ramanarayanan Krishnamurthy (Ramanarayanan Krishnamurthy) of the Scripps Institution in La Jolla (USA).
According to the generally accepted theory today "RNA world", the role of proteins and DNA in the first living organisms on earth playing an RNA molecule. As a consequence of cellular processes began to control proteins and the role of genetic information storage took DNA. Today, scientists are experimenting with short RNA molecules, trying to reproduce the process of the origin of life in the laboratory.
In particular, the molecular evolutionary biologists are now trying to understand how RNA molecules have been replaced by their DNA analogues. Most scientists assume that this happened gradually - at first appeared so-called "chimeras", a molecule consisting of units of RNA and DNA, and then the RNA nucleotides have been gradually supplanted by our usual "letters" contained in our genetic code.
Krishnamurti and his colleagues have found that it is most likely could not take place in reality, examining the extent to which these will be stable chimeric "hybrids" of DNA and RNA. To this end, scientists have collected a few short chains of "pure" DNA and RNA molecules, made up of 16, 10 and 6 "letters" -nukleotidov.
Some of these molecules researchers treated such that some of the "letters" in them become analogues used in RNA or DNA, whereby they become chimeric "hybrids," the likes of the "building blocks of life," which existed during the generation of life. Having prepared solutions of such "chimeras", the authors of the article is heated them and followed up with how quickly they decompose.
It was found that the addition of even one foreign "letters" led to a sharp decrease in the stability of the molecules, reducing its decomposition temperature by 10-20 degrees Celsius. A similar response was observed in the DNA molecules and RNA molecules with changes in all types of letters and the connections between them, which means that all chimeras are extremely unstable in nature.
Their volatility, as recognized by Krishnamurti, does not mean that they can not exist in principle in the primary "soup" Earth's oceans, but their existence in the first living cells, would require the presence of complex enzymes which would permanently "repaired" such molecules and protect them from decay. It is highly unlikely that they originated before there were the first proteins and DNA.
Therefore, according to Krishnamurti, a smooth transition from the RNA world to modern life was impossible, that gave him the idea that RNA and DNA having at the same time, and that the first life could be used both in his life. Such a scenario is, in his opinion, is more consistent with the experimental results and the fact that we see in modern organisms than a hypothesis "RNA world".
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