Oct 26, 2023 05:53 AM
The “dark biosphere”: Do mirror-image lifeforms exist?
https://bigthink.com/life/dark-biosphere...lifeforms/
INTRO: You’re twisted. Sorry, but we all are. The molecules most central to life twist one way or the other. Your most famous molecule, DNA, a spiraling helix like the thread of a screw, is right-handed. The molecules encoded by your DNA, proteins, are left-handed. Even humble sugars like glucose have a twist to their shape.
Why does this handedness, called chirality after the Greek word for hand, feature in the molecules (clusters of atoms) from which all life on Earth is constructed? How and when was the left-or-right chiral twist of life’s components decided? No one knows—even though the chirality of life has been recognized for more than a century and a half.
But we do know that living organisms are exquisitely sensitive to this handedness. Feed bacteria with left-handed amino acids, and they’ll incorporate them into their proteins. Feed them right-handed amino acids, and they are likely to ignore them, even though these are the same molecules but inverted as though in a mirror.
Maybe we just need to accept this is how life is. It exists on one side of the looking glass. But some researchers think there could be equivalent lifeforms on the other side too—if only we could make them. They are already making mirror-image versions of proteins and nucleic acids like DNA. These molecules could be valuable drugs—all the more effective because their looking-glass structure should allow them to operate out of sight of the body’s usual defense mechanisms for breaking apart foreign molecules.
But biochemist Ting Zhu of Westlake University in Hangzhou, China, is determined to go much further than that. He’s made it his mission to create mirror-image versions of the key molecular ingredients of life. In principle, it might be possible to assemble those components into synthetic cell-like entities that can replicate and metabolize: a kind of primitive form of life, but inverted relative to every known organism, and therefore the first truly non-natural life form.
“I believe there are many alternative possibilities for life,” says Zhu. “But among all of these, there is one that we know for sure would work, and that’s the exact mirror-image version of ourselves.” No one knows how such mirror-image cells would get along with ordinary ones—maybe they’d ignore each other, or compete? Might our planet have already conducted a version of that experiment in the wild, billions of years ago when life began?
Over the past several years, Zhu and his colleagues have performed the monumental task of making, from their constituent molecular parts, mirror-image versions of the key biomolecules in living cells: DNA, its sibling RNA, and the enzymes for replicating them and translating their sequences into proteins. He hasn’t got the full set yet, but he is getting very close. Only a few components are still to be added to the basic biomolecular toolkit needed by stripped-down, minimal versions of mirror-image life... (MORE - details)
Humans and Neanderthals mated 250,000 years ago, much earlier than thought
https://www.livescience.com/archaeology/...an-thought
INTRO: Neanderthals and anatomically modern humans initially interbred 250,000 years ago, a date that is far earlier than previously thought, a new study suggests.
Until now, Neanderthals and anatomically modern humans (Homo sapiens) were believed to have first interbred earlier than 75,000 years ago, according to a 2016 genetic analysis in the journal Nature. However, a new analysis, published Oct. 13 in the journal Current Biology, has revealed that one group of Homo sapiens from Africa interbred with Neanderthals in Eurasia around 250,000 years ago.
This group of humans died out, but left a genetic footprint in the DNA of Neanderthals that descended from this interbreeding event — with 6% of the genome of a Neanderthal discovered in Siberia containing human DNA. Some sub-Saharan populations of anatomically modern humans also inherited Neanderthal DNA when groups of humans who had interbred with Neanderthals migrated back into Africa.
"The enhanced understanding derived from this research will enable us to annotate Neanderthal DNA in modern human genomes, as well as the reverse process, with greater accuracy," Michael Dannemann, an associate professor of evolutionary and population genomics at the University of Tartu in Estonia who was not involved in the research, told Live Science in an email.
This will help scientists predict how interbreeding events impacted the physical characteristics of both groups and improve our understanding of the migration patterns and interactions between modern humans and Neanderthals... (MORE - details)
https://bigthink.com/life/dark-biosphere...lifeforms/
INTRO: You’re twisted. Sorry, but we all are. The molecules most central to life twist one way or the other. Your most famous molecule, DNA, a spiraling helix like the thread of a screw, is right-handed. The molecules encoded by your DNA, proteins, are left-handed. Even humble sugars like glucose have a twist to their shape.
Why does this handedness, called chirality after the Greek word for hand, feature in the molecules (clusters of atoms) from which all life on Earth is constructed? How and when was the left-or-right chiral twist of life’s components decided? No one knows—even though the chirality of life has been recognized for more than a century and a half.
But we do know that living organisms are exquisitely sensitive to this handedness. Feed bacteria with left-handed amino acids, and they’ll incorporate them into their proteins. Feed them right-handed amino acids, and they are likely to ignore them, even though these are the same molecules but inverted as though in a mirror.
Maybe we just need to accept this is how life is. It exists on one side of the looking glass. But some researchers think there could be equivalent lifeforms on the other side too—if only we could make them. They are already making mirror-image versions of proteins and nucleic acids like DNA. These molecules could be valuable drugs—all the more effective because their looking-glass structure should allow them to operate out of sight of the body’s usual defense mechanisms for breaking apart foreign molecules.
But biochemist Ting Zhu of Westlake University in Hangzhou, China, is determined to go much further than that. He’s made it his mission to create mirror-image versions of the key molecular ingredients of life. In principle, it might be possible to assemble those components into synthetic cell-like entities that can replicate and metabolize: a kind of primitive form of life, but inverted relative to every known organism, and therefore the first truly non-natural life form.
“I believe there are many alternative possibilities for life,” says Zhu. “But among all of these, there is one that we know for sure would work, and that’s the exact mirror-image version of ourselves.” No one knows how such mirror-image cells would get along with ordinary ones—maybe they’d ignore each other, or compete? Might our planet have already conducted a version of that experiment in the wild, billions of years ago when life began?
Over the past several years, Zhu and his colleagues have performed the monumental task of making, from their constituent molecular parts, mirror-image versions of the key biomolecules in living cells: DNA, its sibling RNA, and the enzymes for replicating them and translating their sequences into proteins. He hasn’t got the full set yet, but he is getting very close. Only a few components are still to be added to the basic biomolecular toolkit needed by stripped-down, minimal versions of mirror-image life... (MORE - details)
Humans and Neanderthals mated 250,000 years ago, much earlier than thought
https://www.livescience.com/archaeology/...an-thought
INTRO: Neanderthals and anatomically modern humans initially interbred 250,000 years ago, a date that is far earlier than previously thought, a new study suggests.
Until now, Neanderthals and anatomically modern humans (Homo sapiens) were believed to have first interbred earlier than 75,000 years ago, according to a 2016 genetic analysis in the journal Nature. However, a new analysis, published Oct. 13 in the journal Current Biology, has revealed that one group of Homo sapiens from Africa interbred with Neanderthals in Eurasia around 250,000 years ago.
This group of humans died out, but left a genetic footprint in the DNA of Neanderthals that descended from this interbreeding event — with 6% of the genome of a Neanderthal discovered in Siberia containing human DNA. Some sub-Saharan populations of anatomically modern humans also inherited Neanderthal DNA when groups of humans who had interbred with Neanderthals migrated back into Africa.
"The enhanced understanding derived from this research will enable us to annotate Neanderthal DNA in modern human genomes, as well as the reverse process, with greater accuracy," Michael Dannemann, an associate professor of evolutionary and population genomics at the University of Tartu in Estonia who was not involved in the research, told Live Science in an email.
This will help scientists predict how interbreeding events impacted the physical characteristics of both groups and improve our understanding of the migration patterns and interactions between modern humans and Neanderthals... (MORE - details)
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