Theoretical origin of life; why RNA world couldn't work (Introduction)

by David Turell , Friday, June 26, 2015, 20:34 (3438 days ago) @ David Turell

Another review of the theory. It has a chicken and egg problem of what came first. Remember all of the research is intelligently designed in a complex lab:-
http://www.newscientist.com/article/mg22630273.700-why-rna-world-theory-on-origin-of-life-may-be-wrong-after-all.html#.VY2uhGDbK1s-"Life has a chicken-and-egg problem: enzymes are needed to make nucleic acids - the genetic material - but to build them you need the genetic information contained in nucleic acids. So most researchers assume that the earliest life, long before the evolution of cells, consisted of RNA molecules. These contain genetic information but can also fold into complex shapes, so could serve as enzymes to help make more RNA in their own image - enabling Darwinian evolution on a molecular level.-"At some point, the idea goes, this RNA world ended when life outsourced enzymatic functions to proteins, which are more versatile. The key step in this switch was the evolution of the ribosome, a structure that builds protein molecules from genetic blueprints held in RNA.-"But such a transition would require abandoning the enzymatic functions of RNA and reinventing them in proteins. "That is not a simple model," says Loren Williams, a biochemist at the Georgia Institute of Technology in Atlanta.-"Williams has further reason to question the RNA world. His detailed study of the ribosome shows that its most ancient part, which is identical in every living thing, acts as an enzyme to link amino acids in a growing protein chain. But this ribosomal core works pretty badly, Williams told the Astrobiology Science Conference in Chicago last week, and so is unlikely to be the product of a long period of evolution by natural selection.-****-"How would this have worked? Nick Hud, also at Georgia Tech, has an idea. Modern proteins and RNA don't assemble on their own, but Hud has found relatives of each that do, spontaneously forming protein-like molecules up to 14 amino acids long as well as gene-like rows of proto-RNA, he reported at the same conference.-"In Williams's scenario, these crude proto-proteins and proto-RNA would have happened to form a ribosomal core, which helped accelerate the random assembly of more protein and RNA molecules (see diagram). "This is the origin of life. I think this came before replication," says Williams.-***-"If Williams is right, RNA has cooperated with proteins from the very beginning. "This marriage between RNA and protein is the most ancient and fundamental part of biology," he says. If so, those who are trying to build self-replicating RNA molecules in the lab are looking for something that never existed.-"Not everyone agrees with this idea, however. "There are other reasons to expect a complex RNA world," says Steven Benner at the Foundation for Applied Molecular Evolution in Florida. Many modern protein enzymes, for example, have RNA associated with them that serves no functional role. This implies that they must be relics from a time when RNA was the only thing around, he says.-"Williams is now synthesising what he thinks is the most ancient ribosomal core, free of all its later add-ons, to test whether it really assembles RNA and protein molecules."