Did Life Emerge in the “Primordial Soup” via DNA or RNA? Surprising Answer From New Research

Primordial Soup Concept

Scientists have long debated which genetic information carrier — DNA or RNA — started life on Earth, but a new study suggests life could have begun with a bit of both. The research, led by scientists from the Medical Research Council (MRC) Laboratory of Molecular Biology (LMB), in Cambridge, shows for the first time how some of the building blocks of both DNA and RNA could have spontaneously formed and co-existed in the ‘primordial soup’ on Earth.

The work challenges one of the leading hypotheses for the advent of life — the ‘RNA world’ theory, which arose in the 60s and has gained wide acceptance.

Today, all known living organisms use the same genetic molecules — called nucleic acids — to store information. There are two sorts of nucleic acids: DNA and RNA. DNA encodes instructions in genes. Genes are turned into messages using RNA, which carries instructions to make proteins. Proteins can make structures and act as molecular machines.

In the ‘RNA world’ theory, life started with RNA molecules, which can both store instructions and can act as a modest machine, potentially enabling them to self-replicate. It proposes that through evolution, life in the RNA world gave way to the era of DNA and proteins, because DNA is more stable and durable than RNA.

In the current study, published in Nature, the researchers simulated the conditions on a primordial rocky Earth with shallow ponds in the lab. They dissolved chemicals that form RNA in water, then dried them out and heated them, then they simulated the early sun’s rays by exposing them to UV radiation.

In this recreation of early Earth geochemistry, intermediates in the synthesis of two of the building blocks of RNA were simultaneously also converted into two of the building blocks of DNA.

It is the first demonstration that reasonable amounts of a genetic alphabet made up of four building blocks, two for RNA and two for DNA — potentially sufficient to have encoded early life, which was far less complex than life today — may have been available on the primordial Earth.

Professor John Sutherland from the MRC Laboratory of Molecular Biology, who led the work, says: “The RNA world hypothesis suggests that life began with RNA, before a genetic takeover occurred involving primitive biosynthetic machinery and natural selection to result in DNA.”

“Our work suggests that in conditions consistent with shallow primordial ponds and rivulets there was a mixed genetic system with RNA and DNA building blocks co-existing at the dawn of life. This fulfills what many people think is a key precondition for the spontaneous emergence of life on Earth.”

The team’s experiments to simulate early Earth geochemistry showed that four of the building blocks for DNA and RNA can arise from the same reagents and conditions. They produced cytidine and uridine, two of the building blocks of RNA, and deoxyadenosine, which is one of those of DNA. Deoxyadenosine was partly converted to deoxyinosine, which can take the role of another DNA building block.

They believe that these four building blocks may have coexisted before life evolved and were the beginnings of a primitive genetic alphabet.

Professor Sutherland adds: “The nucleic acids, RNA and DNA, are clearly related and this work suggests that they both derive from a hybrid ancestor, rather than one preceding the other.”

“Since genetic information always flows from nucleic acids to proteins, and never in reverse — a principle called the ‘central dogma’ of molecular biology by Francis Crick — we now need to uncover how the information which can be stored and purveyed by these nucleic acids could have been first used to make to proteins.”

Understanding the chemical origins of life is a fundamental aspect of natural science, and can inform the design of future synthetic biology.

Dr. Megan Dowie, head of molecular and cellular medicine at the MRC commented: “This study shows that blue skies research can reveal fascinating insights into how the very beginnings of life may have emerged, and demonstrates the importance of supporting fundamental research. These underpinning discoveries in the life sciences could enable exciting future strategies for artificial biology.”

Reference: “Selective prebiotic formation of RNA pyrimidine and DNA purine nucleosides” by Jianfeng Xu, Václav Chmela, Nicholas J. Green, David A. Russell, Mikołaj J. Janicki, Robert W. Góra, Rafał Szabla, Andrew D. Bond & John D. Sutherland,3 June 2020, Nature.
DOI: 10.1038/s41586-020-2330-9

4 Comments on "Did Life Emerge in the “Primordial Soup” via DNA or RNA? Surprising Answer From New Research"

  1. Sekar Vedaraman | June 7, 2020 at 8:45 pm | Reply

    I agree.

    Fundamental basic research has been badly underfunded for a very long time, as the financial benefits from the same is not visible immediately, and very few private sector organizations whose exisence is dependent on the ability to grow revenues and profits and make quarterly forecasts can make such investments next to impossible.

    Humanity’s very existence and future progress depends on continuing funding of basic scientific research. Many of the breakthroughs benefits may not be immediately visible to most people in the private sector, whose vision is seen through rose tinted financial glasses. Also the Research Findings real benefits and breakthroughs may not be visible for many generations and the applicability of the research methodology across various specialized disciplines is also badly underestimated.

    Science and Scientific Progress based on evidence will determine the future of Humanity.

    Another , extraordinary and important realization which is not emphasized is the fact that almost nine out of ten experiments do not result in success but failure, just like nine out of ten new buisnesses fail. People fail to understand that each failure is itself very valuable information, as failure analysis and determining the root cause of the failure is the very basis for future success , both in Scientific Experiments and New Buisness Creation.

    Only the people who have understood this basic reality and the importance of th willingness to take risk will survive and prosper.

    Another forgotten fact is the reality, that No Failure or Success is permanent. This is true for Scientific Research and Findings as it is for New Buisnesses started.

  2. Nadia Bessamra | June 8, 2020 at 4:23 am | Reply

    Thanks.

  3. Very interesting and informative article. I hope they will continue to move forward with this research. I would be interested to see what type of life forms from their prebiotic soup and if they can determine how all the various forms of life were created.

  4. I told you theory years ago: take the biggest ocean on amino acids and do what you like with it – you won’t get anything remotely suggesting life. This accidental hypothesis requires a lot more faith than the obvious so: full marks for faith.

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