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Biotech Science

'Monumental' Experiment Suggests How Life on Earth May Have Started (pressherald.com) 127

An anonymous reader shared this article from the Washington Post: A much-debated theory holds that 4 billion years ago, give or take, long before the appearance of dinosaurs or even bacteria, the primordial soup contained only the possibility of life. Then a molecule called RNA took a dramatic step into the future: It made a copy of itself. Then the copy made a copy, and over the course of many millions of years, RNA begot DNA and proteins, all of which came together to form a cell, the smallest unit of life able to survive on its own.

Now, in an important advance supporting this RNA World theory, scientists at the Salk Institute for Biological Studies in La Jolla, Calif., have carried out a small but essential part of the story. In test tubes, they developed an RNA molecule that was able to make accurate copies of a different type of RNA. The work, published in the journal Proceedings of the National Academy of Sciences, gets them closer to the grand goal of growing an RNA molecule that makes accurate copies of itself.

"Then it would be alive," said Gerald Joyce, president of Salk and one of the authors of the new paper. "So, this is the road to how life can arise in a laboratory or, in principle, anywhere in the universe...."

John Chaput, a professor of pharmaceutical sciences at the University of California at Irvine who did not participate in the study, called the crossing of that threshold by the Salk team "monumental," adding that "at first, I looked on it as a little bit jaw-dropping. ... It's super-neat."

The Post adds that "the scenario they tested probably mimics one of the earliest stirrings of evolution." And Michael Kay, a professor of biochemistry at University of Utah, says the new paper has given the RNA World theory "key evidence" to show "it is plausible and reasonable." He added that the RNA copier developed at Salk will "provide a valuable tool for people wanting to do directed evolution experiments."
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'Monumental' Experiment Suggests How Life on Earth May Have Started

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    • Re: (Score:3, Funny)

      by Anonymous Coward

      But... it was aliens.

      No, it was GOD, y'know your invisible intelligent creator in the sky. He created the world, then he created all life, then he created man from a mud sculpture and finally he took one of the man's rib and transcoded his male DNA to create woma ... wait, ... that means ... women are ... uhh ... transcoded men?? ... uhh ... n-never mind ... I need to go re-examine my entire world view.

      • Yeah the whole "magical super-being crafting the universe from nothing" makes so much more sense than all that sciency stuff.

  • Reading the paper, it took scientists 10-years to develop (not sure of procedure) hammerhead RNA which is now able to copy itself.

    The origin of the RNA in this story is lab created RNA.

    Electronic Arts promised me a molecule construction set back in the 90's, where is it?

    • 10 years is all? The planet had (literally) zillions of chemicals randomly mixing in diverse and fucked up conditions for 500 million years before the first cell life emerged. The Earth timeline according to phylogenetic studies and paleontology record is (if I recall correctly .. please fact check): Earth formation --- 500 million years pass --> single cell life emerges --500 million years go by--> last universal common ancestor (LUCA) --1 billion years--> multicellular life --1 billion years--

  • Living is a verb (Score:5, Insightful)

    by LeDopore ( 898286 ) on Sunday March 10, 2024 @10:52AM (#64304323) Homepage Journal

    Hats off to understanding more about RNA world and how it might have worked. That's great. That said, a growing number of physicists like me think that RNA world could not have been the first life as the headline implies. There's a debate between genome-first and metabolism-first scientists, and I fall into the latter camp. We think metabolism of some kind probably predated RNA. Here's why.

    RNA is cool because it can both catalyze reactions and act as a template for making more of itself. Each sugar has an extra hydrogen bond (compared to DNA) which makes RNA able to twist into functional shapes kind of like enzymes, but RNA can also serve as a template for a complementary strand to be made. RNA thus can do a half-assed job of both of DNA and of proteins, and RNA is an intermediate in the DNA -> RNA -> protein synthesis that happens in today's cells, so it's very likely to have been a precursor to both DNA and proteins, and avoids a lot of chicken-and-egg problems with all three having to appear at the same time.

    That said, lots of physicists today are pretty confident that the first life had to include some form of metabolism: a channel through which free (i.e. low-entropy) energy is flowing. Any chemical reaction in thermodynamic equilibrium will by definition progress as fast forwards as backwards. "Life" without free energy would statistically be exactly as likely to shrink as to grow in size. Suppose there were a soup of elements at equilibrium and you added RNA to it. It would just sit there or decompose; without a source of free energy any movie of what it does would necessarily be equally likely played forwards or backwards. That's what equilibrium means.

    The first life therefore almost certainly was linked to some inorganic source of free energy; probably geochemical in origin. Molecules that shape the chemical reactions in specific, contagious ways would tend to propagate to the limits of the source of free energy. At some point, RNA probably became the dominant molecule enabling metabolism with contagious specific properties, but without the flow of free energy, you'd get no propagation.

    Living is a verb. I'd even say that "metabolism with contagious specific properties" might be an interesting definition for life. (NASA's current definition is "a self-sustaining chemical system capable of Darwinian evolution" but self-sustaining discounts the necessity of the flow of free energy and you might not always have the time to see Darwinism in action. Is my spayed cat alive by NASA's definition? She needs cat food to sustain herself and cannot participate in Darwinian evolution anymore! Yet, her metabolism's specifics can be contagious and infect her cat food, causing its molecules to make more cat in a way the cat specifies.) The idea that the right brew of RNA in the absence of free energy flow and metabolism could "be" life is misguided and doesn't do justice to the centrality of metabolism in understanding what life really is.

    • The headline doesn't imply that RNA was the first form of life.

    • The argument about an energy gradient being required to allow localized reversal of entropy is pointless, because it's such an obvious and necessary assumption it does not normally bear mentioning. The entire universe requires it, so there is almost never any point in mentioning it for smaller scale specific cases unless you're trying to identify locations where the energy gradient is within the range that supports the chemical reactions you are looking for.

      Also, if you abstract your individual cat to the

      • The argument about an energy gradient being required to allow localized reversal of entropy is pointless, because it's such an obvious and necessary assumption it does not normally bear mentioning. The entire universe requires it ...

        I would say a star doesn't require an external energy gradient to keep being a star. It needed free energy to become a star, but it isn't reliant on continued external flows of free energy to keep on being a star.

        Channeling free energy from an external source is a key property of living matter.

        • Natural selection is the key.

          Without replication, metabolism is just a chemical reaction.

          The environment in which the first replication arose might indeed have many support molecules that supply appropriate energy. But they cannot evolve without replication.

          My guess is that the first life was not RNA but something that eventually evolved into RNA.

    • It seems pretty obvious that there was some sort of machinery in place (which by definition might be considered as life) to have created something as complex as RNA. This is basically the concept of assembly theory. If RNA is made in the lab, then humans are the assembler.

      I agree with Stuart Kaufmann's "At home in the universe" that self-perpetuating "metabolisms" would be almost inevitable in the right environment, and this seems infinitely more plausible as the origin of life. RNA would be many steps late

    • probably geochemical in origin

      I disagree. The only regularly changing source of energy is/was the Sun. No geochemical process is likely to have stayed stable long enough to get the changes that were necessary for further evolution. And change is what 'motivates' evolution.

      Everything else you said seems perfectly reasonable.

      • Yes, the Sun is incredibly important as a vast source of free energy. The consensus is that photosynthesis evolved a little bit after life arose (see https://www.ncbi.nlm.nih.gov/p... [nih.gov] for example). There are some geochemical processes like alkaline vents and hot springs that provide a steady enough source of free energy to get life going, but as soon as photosynthesis evolved the Sun became our main meal ticket.

  • Why is RNA special? (Score:5, Interesting)

    by kbahey ( 102895 ) on Sunday March 10, 2024 @12:36PM (#64304557) Homepage

    RNA is different from DNA in a few aspects.

    One of them is that RNA is less stable, and therefore has a higher mutation rate than DNA.
    That is one reason why the Influenza viruses keep changing from season to season, because the flu is an RNA virus.

    Another aspect of RNA, is that in addition to carrying genetic information, it can also act as a catalyst (enzyme).

    So it is a dual tool if you like ...

    Life today still depends on that latter function of RNA: the ribosomes in every living cells depend on RNA's catalytic function for one of the most essential functions: protein synthesis.

    Even after DNA took over, and after eukaryotes evolved (including multicellular life like us), RNA from the RNA World is still around.

    There are also similarities between RNA and certain essential nutrients such as some B vitamins (niacinamide, ...), which suggest common biochemical origins.

  • You could also start with:
      - two molecules that (moderately) accurately copied each other (though getting them both at the same time makes the time scale to the big event much longer.)
      - A molecule that makes NEARLY always inacurate (but occasionally acurate and complete) copies of itself. (This also drastically pulls in the time to a two-molecule solution.)
      - A molecule that makes inaccurate copies but with string of typical errors that occasionally loops back to an accurate and complete (mod a few errors in unimportant places) copy of a previous version.

    These could eventually mutate into a version that can perform a one-step copy-itself loop.

    =====

    I've always been partial to an RNA-only origin. RNA can do it all (self-copy, enzymes, energy transport batteries in at least two sizes with self-pluggin-in connectors: ATP/ADP and UTP/UDP, expression regulation, directed genetic code editing, etc.). It's also still doing a lot of that in current lifeforms, especially in key parts (such as many of the components of the DNA duplication, DNA repair, DNA-to-MRNA copy, gene expression regulation, MRNA exon-eliminating editing, and MRNA directed protein synthesis machinery)

  • > gets them closer to the grand goal of growing an RNA molecule that makes accurate copies of itself.

    One interesting hypothesis is that the first life didn't replicate itself directly, but produced a complementary part which then was able to produce the original design: an A-B-A-B-A-B-etc. pattern. The complementary parts would work in tandem to collect and process energy toward reproduction: symbiosis.

    This may be more likely because self copying is often pretty tricky. Producing something easier that la

Think of it! With VLSI we can pack 100 ENIACs in 1 sq. cm.!

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