A Chemical Path to the RNA World Is Revealed

May 17, 2016 | Erica Tennenhouse

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Photo credit: Jose Maria Cuellar/flickr (CC BY-NC 2.0)

Honing in on the origins of life on Earth.

At a certain point in Earth’s history, the first signs of life arose from nonliving material. Exactly how life originated is not easy to pin down, as the ancient ancestor to all living creatures remains somewhat elusive.

The prevailing opinion among scientists is that about 4 billion years ago, RNA — a molecule similar to DNA — arose. The RNA World hypothesis posits that RNA was the very first biological molecule, and the precursor to all modern life on Earth.

Scientists have been on the lookout for evidence supporting the RNA World hypothesis for some time. For the idea to hold weight, it would be necessary to show that the building blocks of RNA — the nucleotide bases uracil, cytosine, adenine, and guanine — could have formed under the conditions that existed on early Earth.

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It has been relatively easy for scientists to demonstrate how two of the components of RNA, uracil and cytosine, came about during that period. But adenine and guanine are more chemically complex molecules, and until now, it has been unclear how they could have arisen from the early Earth’s primordial soup.

In a paper published in the journal Science, chemists at Ludwig Maximilian University of Munich described their successful replication of chemical pathways that could have plausibly given way to both adenine and guanine in a prebiotic world.

RNA is considered the best candidate for the precursor of life because it is able to store, transmit, and replicate genetic information, just like DNA. But unlike DNA, it can also act as an enzyme by building proteins. Together, these traits would have potentially allowed RNA to support the very first independent life forms.

By lending support to the RNA World hypothesis, these new findings bring us one step closer to uncovering our most ancient ancestor — the life form from which all organisms on the planet are descended.

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