(ORDO NEWS) — The question of how life began on Earth continues to interest scientists, but it is not easy to look into the past billions of years. There is now growing evidence of a relatively new hypothesis about how life began: with a very precise combination of RNA and DNA.
Both RNA and DNA determine the genetic makeup of all biological life, with DNA acting as the genetic blueprint and RNA as a blueprint reader or decoder. For a long time, it was believed that RNA first arose on Earth, and then DNA evolved, but new data indicate that they may have arisen simultaneously, and both participated in the origin of life on the planet.
The latest research supporting this idea explains how a simple compound diamino phosphate (DAP), which predates life on Earth, can combine DNA building blocks called deoxynucleosides into DNA backbones.
“This discovery is an important step towards the development of a detailed chemical model of how the first life forms arose on Earth,” said chemist Ramanarayanan Krishnamurthy of Scripps Research in California.
The findings support the idea that both DNA and RNA arose together as a result of the same chemical reactions early in life on our planet, and that the first self-replicating molecules could have been mixtures of both of these nucleic acids, and not just RNA, as is assumed in the more established hypothesis of the “RNA world”.
One of the big problems with the idea that RNA alone gave rise to life on Earth is how RNA was able to undergo the necessary self-replication process – RNA usually requires the cleavage of enzymes that evolved after RNA.
From what we know so far, it seems that RNA helped in some way to engineering life – and recent experiments show that DNA could well create “chimeric” molecular chains that separate more easily than RNA alone.
A series of laboratory tests conducted by the researchers modeled what could have happened before life on Earth began and show how basic DNA could have formed in much the same way that RNA can be assembled from chemical building blocks.
“To our surprise, we found that using the deoxynucleoside reaction works better when the deoxynucleosides are not all the same, but a mixture of different DNA letters, like A and T or G and C, like real DNA,” says biologist Eddie Jimenez from Scripps Research.
We may never know for sure if RNA DNA helped shape the first life forms on our planet, given that this happened billions of years ago, but our understanding of these processes continues to evolve.
Research is useful not only in terms of how it relates to the origin of life – understanding the RNA-DNA relationship has many applications in modern chemistry and biology.
“Now that we better understand how primitive chemistry could create the first RNA and DNA, we can start using it in mixtures of the building blocks of ribonucleoside and deoxynucleoside to see which chimeric molecules form – and if they can replicate and develop themselves,” says Krishnamurti …
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