Molecules of DNA and RNA arose at the same time.
Biologists from the United States found evidence of alternative options for the development of life on Earth, in which it is assumed that DNA and RNA molecules emerged at the same time, bypassing the stage of RNA-world.
The findings of scientists was published in the journal Angewandte Chemie. By General theory, the role of DNA and proteins in the first living organisms on Earth played RNA. Later, the cellular processes begin to control proteins, and the role of the information store started playing DNA. At the moment, researchers are trying to understand how the process of substitution of the RNA molecules to their DNA counterparts. According to scientists, this process occurred gradually: first there was the so-called “Chimera” molecule, consisting of links and of RNA and DNA, and then RNA nucleotides were gradually replaced by “letters” contained in the human genetic code. In the new study, scientists have tracked how sustainable will such a “Chimera” in the real world. To do this, scientists have collected a few short chains of “pure” DNA and RNA molecules, composed of 16, 10 and 6 “letters”-nucleotides.
Of these molecules, scientists treated in such a way that some “letters” in them became the analogues used in RNA or DNA, with the result that they became chimeric “hybrid”, likes those “blocks of life” that existed during the origin of life. Preparing solutions of such “chimeras”, the authors heated them and saw how quickly they decayed. It turned out that even adding one “letter” led to a sharp decrease in lifetime of the molecule, lowering the temperature of its disintegration by 10-20 degrees Celsius.
A similar reaction was observed in the molecules DNA and RNA, and evidence that such “chimeras” are unstable by nature. The researchers emphasize that the instability of these compounds does not indicate that they do not exist in principle, but their existence in the first organisms on Earth require a complex of enzymes that are constantly “repaired” to such cells and protect them from decay. It is highly unlikely that they originated before the advent of DNA.
Therefore, according to the researchers, the transition from the RNA world to the emergence of DNA impossible, what gave them the idea that DNA and RNA arose at the same time, and the first life is used both in the course of its evolution.
