For more than half a century, biochemists have been discovering more and more new ways of nucleation of the RNA molecule in simple chemical reactions. Their diversity is so great that many experts adhere to the RNA World hypothesis. According to her, at the time of prebiotic evolution, the period of the appearance of the first organic compounds, RNA molecules have long existed. Simply because even the statistical probability of their occurrence is very high. But what about DNA?
The DNA molecule is a derivative of RNA, it is more complex and has a lower chance of "survival". At the same time, a recent study by American and British chemists showed that RNA can be converted to DNA in just a few simple steps, even without the use of enzymes. The problem is that transitional forms, hybrid versions of RNA, are several times less stable than pure DNA and RNA molecules.
It turns out that even though DNA could be formed from RNA, the chances of its preservation were slim. But chemist Ramanarayanan Krishnamurti of the American Scripps Research Institute has a different opinion. He discovered the ability of the sulfurous substance thiuridine to react with deoxyadenosine, the sugar backbone of the RNA molecule. And one of the results of this reaction is the formation of a deoxyribose compound, which can lead to the appearance of DNA.
This prompted Krishnamurti to think that there were no pure and stable molecules in the "RNA World". On the contrary, the great similarity and propensity for interconversion indicate a common ancestor of DNA and RNA, which was weak and unstable. And in the course of evolution, it developed into two similar, but still different molecules that exist in parallel. And yes, it really could have happened even before the appearance of life in the "primary soup", as experts call that prehistoric environment.