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Biology: Are cosmic rays why life "prefers" right-handed DNA and RNA?

Introversion

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Lopsided interactions between cosmic-ray particles and chiral biomolecules may explain why all life on Earth relies exclusively on right-handed DNA and RNA helixes.

Quanta Magazine said:
If you could shrink small enough to descend the genetic helix of any animal, plant, fungus, bacterium or virus on Earth as though it were a spiral staircase, you would always find yourself turning right — never left. It’s a universal trait in want of an explanation.

Chemists and biologists see no obvious reason why all known life prefers this structure. “Chiral” molecules exist in paired forms that mirror each other the way a right-handed glove matches a left-handed one. Essentially all known chemical reactions produce even mixtures of both. In principle, a DNA or RNA strand made from left-handed nucleotide bricks should work just as well as one made of right-handed bricks (although a chimera combining left and right subunits probably wouldn’t fare so well).

Yet life today uses just one of chemistry’s two available Lego sets. Many researchers believe the selection to be random: Those right-handed genetic strands just happened to pop up first, or in slightly greater numbers. But for more than a century, some have pondered whether biology’s innate handedness has deeper roots.

“This is one of the links between life on Earth and the cosmos,” wrote Louis Pasteur, one of the first scientists to recognize the asymmetry in life’s molecules, in 1860.

Now two physicists may have validated Pasteur’s instincts by connecting the unvarying twist in natural DNA with the behavior of fundamental particles. The theory, which appeared in May in The Astrophysical Journal Letters, doesn’t explain every step of how life acquired its current handedness, but it does assert that the shape of terrestrial DNA and RNA is no accident. Our spirals might all trace back to an unexpected influence from cosmic rays.

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MaeZe

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Might have been fun for the X-files to use left-handed DNA instead of "branched DNA" which made no physiological sense to any biologists. :D
 

Chris P

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And not only right handed DNA and RNA, but only L-amino acids, and not D, are produced by biological systems. Those produced abioticly are a mixture of D and L. Just as the DNA could just as easily be right or left handed, but only right occurs. That's how, in theory, an identified amino acid of extraterrestrial source is determined to be biologically produced versus chemically: a D and L mixture is chemical, all L or all D is biological. I have yet to hear a satisfactory answer, and I'm not sure cosmic rays will do it. I'll need to see a mechanism for how cosmic rays would direct the assembly. Biologist that I am, the evolutionary founder's principle of one arising first by chance and setting the stage comes closest for me.

With the advent of synthetic biology (by whatever definition folks eventually settle on) I'd like to see left-handed DNA synthesized and see how it codes for proteins, or make synthetic proteins of D-amino acids and see what happens. Perhaps someone already has.
 
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