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Science

Physicists Find Clue as To Why the DNA Double Helix Twists To the Right 120

Posted by samzenpus from the no-southpaws-in-lfe dept.
New submitter Annanag writes Most organic molecules have left- or right-handed versions, mirror images of each other, just like gloves. For some reason, life always seems to favor one version over the other — the DNA double helix in its standard form always twists like a right-handed screw, for example. But why this preference for left or right happens has always been a mystery. Now, in an experiment that took 13 years to perfect, physicists have found hints that this asymmetry of life could have been caused by electrons from nuclear decay in the early days of evolution.
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Physicists Find Clue as To Why the DNA Double Helix Twists To the Right More

Physicists Find Clue as To Why the DNA Double Helix Twists To the Right

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  • Man oh man (Score:5, Funny)

    by 93 Escort Wagon ( 326346 ) on Friday September 26, 2014 @01:59AM (#48000439)

    Nowadays it seems like almost everything is twisting to the right...

    • Re:Man oh man (Score:5, Funny)

      by Chrisq ( 894406 ) on Friday September 26, 2014 @03:24AM (#48000693)

      Nowadays it seems like almost everything is twisting to the right...

      Including the iPhone 6....

    • Dog is right-handed of course.

    • Re: (Score:1)

      by quenda ( 644621 )

      It simply proves that God is right-handed.

  • Which side is upwards? (Score:1)

    by Anonymous Coward

    Just flip it, it twist to the left, isn't it?

    • Re:Which side is upwards? (Score:5, Informative)

      by Anonymous Coward on Friday September 26, 2014 @02:38AM (#48000583)

      Nope. A helix [wikipedia.org] has an intrinsic twist direction invariant from the point of view.

      Check it yourself. Get two identical springs and put them side by side, flip one and voila you have the same configuration than before.

    • Re: (Score:2)

      by Richy_T ( 111409 )

      And then a step to the right?

    • Why "right-handed"? Shouldn't it be "clockwise"?

      Twisting towards the right hand could be "over the top" (clockwise) or "around the bottom" (counterclockwise). Not to mention that unless you specify whether you're twisting down the strand towards or away from you (assuming the strands are pointed straight away from your body), means you end up with 4 ways to arrive at 2 possible orientations.

      I suppose the scientific response is, "No, shut up; we just defined this confusing and nonstandard wording as X."

      • Why "right-handed"? Shouldn't it be "clockwise"?

        In a world of digital time devices, that makes no sense :-)

      • Why "right-handed"?

        I suppose the scientific response is, "No, shut up; we just defined this confusing and nonstandard wording as X."

        Pretty much, but it is a bit more complicated that that. Right hand rule refers to the cross product dealing with current, magnetic force, and the way it is taught. Essentially, physics follows a pattern that is mimicked by using the right hand and assigning certain related forces and fields to the thumb and fingers. This is known as the Right Hand Rule [wikipedia.org].

        • Looks like my guess was wrong then--that article seems to indicate that "to the right" = "counterclockwise" for some applications.

          When we already have an unambiguous term to describe something, co-opting an ambiguous one instead is foolish.

          And we all know that the entire field of mathematics is "because we said so" anyway so I suppose I shouldn't be surprised ;)

  • When will they find out why certain part of male anatomy seems to be twisting to the left for majority of us?

    • Re: (Score:3, Funny)

      by Anonymous Coward

      I am lefthanded and mine twists to the right - my theory is it will usually point opposite of your prefered hand and my reason is furious masturbation.

      • my reason is furious masturbation

        While there's something to be said for angry make-up sex, maybe you ought to calm down a bit before taking care of business. You could hurt yourself, lad.

    • Re: (Score:1)

      by Anonymous Coward

      Hint: It's related to most of us being right-handed.

    • When will they find out why certain part of male anatomy seems to be twisting to the left for majority of us?

      Most of us are right handed? ;-)

      • Re: (Score:2)

        by dave420 ( 699308 )
        What about for those of us who are ambiwanxtrous?

        • What about for those of us who are ambiwanxtrous?

          LOL ... assuming my bullshit hypothesis is true ... if you do them equally, no twist at all, if you preferentially use the left hand, twist to the right.

          You'd probably need accurate statistics on if you have a greater, um, usage with one or the other over your lifetime. Frequency, duration, and ... er ... grip strength/technique probably play a factor.

          Now, please do us all a favor, and keep the answer to yourself. ;-)

          Because, too much fscking information.

  • Random chance more likely (Score:1, Interesting)

    by Anonymous Coward

    Mutations happen randomly. A mutation occurs in Right-Version that's beneficial and so the right version becomes the dominant version, nothing to do with right or left, its simply the version that got the beneficial mutation.

    So evolution would drive nature to choose left or right versions of every little enzyme, molecule and so on, simply because it grows from benefitial branches and they are either left or right but not an even mix of both.

  • They forgot a simpler and perhaps more prominent selective force for one enantiomer over another: average experienced twist on the earliest nucleic acid chains from ocean currents. It should be slightly one way, due to Coriolis forces. Did life start North or South of the equator?

    • Did life start North or South of the equator?

      We don't know that.

      The magnitude of forces generated from this force is far below what is around in the environment from random motions.

  • ... before there was life?

    • Re:So evolution possibly already happened ... (Score:5, Insightful)

      by osu-neko ( 2604 ) on Friday September 26, 2014 @03:47AM (#48000751)
      Depending on how you define "life", yes. In fact, almost certainly, regardless of which definition of "life" you choose. Selection can occur in any kind of chemical or physical process in which produces similar but not always identical results. There's nothing special about the particular chemical processes we call "life", nor some magic line in the sand you can draw and say "this is life, and this isn't" -- it gets rather fuzzy on the edges, and the distinction between life and other chemical processes is as arbitrary as the distinction between which celestial bodies we decide to call "planets" and which we decide don't qualify. Nature doesn't care much for our arbitrary distinctions.

      • Re: (Score:2)

        by GuB-42 ( 2483988 )

        ...as arbitrary as the distinction between which celestial bodies we decide to call "planets" and which we decide don't qualify. Nature doesn't care much for our arbitrary distinctions.

        Pluto, is that you ? Don't be bitter, you knew it was inevitable.

      • All life we know about came from a single origin since all life is based on DNA, RNA and proteins. whatever the origin was it would have had left or right handed DNA and thus so did everything that followed. there's no reason to suppose the need for a bias for one or the other. one of them was going to win. it's like vhs and betamax.

        • As light passes by a sun it is subject to an asymmetric situation where the solar atmosphere is in a magnetice field closer to one pole than another, rotating and having a gradient both radially and with the azimuth. thus there's a strong symmetry breaking effect on this light. On average, for all light passing the sun it's an equal handed effect. But if your planet happens to be subject to light that cam from the left side of the sun versus the right, that light could have a net polarization.

          this effec

      • Re: (Score:1)

        by Tablizer ( 95088 )

        So Pluto is alive? Settled!

    • Re: (Score:3)

      by itzly ( 3699663 )
      Evolution happens as soon as you have a simple molecule that can replicate itself, or at least catalyse some reaction that leads to more copies of itself. If your definition of life does not include self-replicating molecules, then there was evolution before life.

  • Asimov said it first (Score:5, Interesting)

    by Ateocinico ( 32734 ) on Friday September 26, 2014 @04:50AM (#48000923)

    http://en.wikipedia.org/wiki/T... [wikipedia.org]

  • Here's my understanding of the article: In organic chemistry- molecules often have asymmetric shape. Even though their chemical composition is same, their selection of "which bond" about the carbon atom causes "twisted" molecules. So there can exist isomers of compounds (like glucose has, and particularly called as anomer). You can imagine the twisted molecule as a fat roll of putty twisted. So, some parts of putty will be observable from outside (exposed) and some, not that exposed.
    In most of the reactio

  • It SHOULD bend to the right. (Score:5, Funny)

    by Chas ( 5144 ) on Friday September 26, 2014 @05:54AM (#48001097) Homepage Journal

    If it bent to the left, that'd be a bit...sinister. [wikipedia.org]

  • It's due to the rotation of the earth, duh! Those down-under rotate the other way, but they are upside down also, so it compensates.

  • It's the Coriolis effect. Duh.

  • The article is rather dubious really.
    There's an underlying assumption that the symmetry braking of the solution requires an asymmetry in the starting condition.
    If you place a pencil upright it is very unstable and it will fall over. In what direction it will fall depends on the 'background noise' disturbances which can be completely symmetrical - on average.
    So you have a completely symmetrical situation but the outcome will be completely asymmetrical: the pencil falls over in one direction. It is not an int

    • There are now over half a dozen carbon-containing meteorites where a (small) excess of L-amino acids was found, and none where the opposite enantiomer was found to be in excess. Since these meteorites where never in contact with the earth's biosphere (the samples were of course not scraped from the surface), the chance of an evolution of isolated systems into a random chiral direction is already pretty slim.

      • Well, I'll need a lot of convincing to conclude that the asymmetry in amino acids was not due to contamination at some stage.

        • Re: (Score:2)

          by Wdi ( 142463 )

          That is an obvious concern, but also one the examining scientists and their reviewers had... consensus seems to be that these concerns were properly addressed, at least in the later studies.

          • Hi Wdi,

            Do you have a citation for the meteorite work?

            Also, even if there's a slight chiral asymmetry in space rocks, space is a high radiation environment compared to the primordial soup. Tinkerton makes a very good point: when the chiral chemical effects of beta decay are this weak even under lab conditions engineered to maximize their strength, it's hard to imagine this asymmetry would play a significant role in the wild.

          • It's a bit more than a concern, it's distrust because the idea has some attributes I'm suspicious about. Compare it with panspermia theories. These theories were successful primarily because people had problems thinking up ways of how life could spring out of nothing. That by themselves doesn't make them wrong of course, and some may claim that it's unsigntific to use such things as distrust. I disagree.

            On the other hand, if it turns out that electroweak parity breaking does percolate upwards all into chemi

  • It's because we're all descendent from Derek Zoolander.

  • when you change the direction from where you view it it changes direction to the left..... woa dude! Far out

  • Headline: "Force of nature gave life its asymmetry (Score:5, Interesting)

    by radtea ( 464814 ) on Friday September 26, 2014 @08:58AM (#48001665)

    Article:

    The interaction of left-handed electrons with organic molecules is not the only potential explanation for the chiral asymmetry of life.. Meierhenrich favours an alternative â" the circularly polarized light that is produced by the scattering of light in the atmosphere and in neutron stars3. In 2011, Meierhenrich and colleages showed4 that such light could transfer its handedness to amino acids.

    But even demonstrating how a common physical phenomenon would have favoured left-handed amino acids over right-handed ones would not tell us that this was how life evolved, adds Laurence Barron, a chemist at the University of Glasgow, UK. âoeThere are no clinchers. We may never know.â

    The new work is interesting and important, but its primary significance is that it makes future work distinguishing the possible alternatives more challenging. It's also interesting because unlike the other two proposed mechanisms it is a result of the fundamental asymmetry in the weak force rather than an accidental boundary condition, so it implies that life everywhere is more likely than not to be right-handed, whereas the explanations involving magnetic fields will make a universe that's 50/50 right/left.

    • It's also interesting because unlike the other two proposed mechanisms it is a result of the fundamental asymmetry in the weak force rather than an accidental boundary condition, so it implies that life everywhere is more likely than not to be right-handed, whereas the explanations involving magnetic fields will make a universe that's 50/50 right/left.

      TFA goes too far with this idea; which I think is confusing the issue here. While the article focuses on DNA chirality, I think that is going too far up the chain of evolution.

      There were most likely replicating molecules before DNA, and many of the building blocks for life were likely set long before DNA became the preferred genetic coding system.

      What this study says, in the bigger picture, is that the chirality of many classes of molecules in early life may have been influenced by this mild bias in the wea

  • That explains why in Star Trek all intelligent life can interbreed despite evolving separately for billions of years. ;)

    • That explains why in Star Trek all intelligent life can interbreed despite evolving separately for billions of years. ;)

      Actually, they can't. Even Spock's parents had to use medical intervention to make it possible. That said, it is interesting, whether they can interbreed or not, that most of them have the correct genitalia and in the right places to accommodate intercourse.

      • Most of the ones we've seen. But, maybe there's a whole bunch that don't. Either of Spock's parents would have had trouble, medical intervention notwithstanding, making it with a Horta.

  • Electrons are right handed and left brained.

  • Hopefully, somebody will read past all the political jokes to answer this. I understand why the physicists are hypothesizing as to why DNA twists to the right. My question is whether or not the right twist is required for life or could a left twisted DNA led to life? If DNA must twist right for life to exist, does that preclude life on many of the star systems that could support life because the same condition that led to our right twisting DNA was absent?

    • Comment removed based on user account deletion

      • Re: (Score:2)

        by Urkki ( 668283 )

        ... and if right or left twisting DNA could equally support life, then the fact that all DNA is right-twisting suggests that life arose just once (or very few times).

        Well, no. As TFA suggests, "electrons created in the subatomic process known as beta decay are always 'left-handed'. ". It could also be some other influence, but the point I'm trying to make is, even though life would work equally well with both directions, it always gets started with DNA twisted the same way.

        Sort of like, all life on Earth can withstand the atmospheric pressure, all life in this universe could have DNA twisting certain way to better withstand beta decay electrons.

        I'm not sure if this is

  • Okay, so if you look at it in the opposite direction, is it still to the right? Is there a standard starting point, like when we say the right side of a car, we're assuming the orientation is from the driver's point of view. Facing the vehicle from the front would reverse that.

    • As someone else posted above, if you look at it from the opposite direction, it still twists right.

      Find the nearest screw or bolt (almost all will be right-handed), pick an end to be up, point your right thumb in that direction then curl your fingers: your fingers will curl in the same direction that is needed to move up the spiral. Now flip the bolt or screw upside down and try it again... Yep, still works. Now try it with your left hand: your fingers will curl in the downwards direction. That is what i

  • DNA is shown as a helix to make it more appealing to the eye.

    The proles don't want to see "a mishmash of random looking scientifical crap".

    Rendering DNA in the form of a double helix makes it purty and romantical and radio-friendly.

  • Lefty-Loosey

    • Only for one type of bolt ; the others are righty-loosey, lefty-tighty. If you work with them (flammable versus non-flammable gasses, left-hand wheels versus right-hand wheels on vehicles), then it is really, really important to make sure that you're doing it right. I routinely send trainees out to change a gas bottle which I know is righty-loosey, with a spanner too short to cause harm, purely to teach them the lesson.

  • Scientists find a clue as to why the chicken crossed the road.

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