28 Facts About RNA world

RNA world is a hypothetical stage in the evolutionary history of life on Earth, in which self-replicating RNA molecules proliferated before the evolution of DNA and proteins.

The concurrent formation of all four RNA world building blocks further strengthened the hypothesis.

Regardless of its plausibility in a prebiotic scenario, the RNA world can serve as a model system for studying the origin of life.

RNA world proposed a scenario whereby the critical electrochemistry of enzymatic reactions would have necessitated retention of the specific nucleotide moieties of the original RNA-based enzymes carrying out the reactions, while the remaining structural elements of the enzymes were gradually replaced by protein, until all that remained of the original RNAs were these nucleotide cofactors, "fossils of nucleic acid enzymes".

RNA world is known to form efficient catalysts and its similarity to DNA makes clear its ability to store information.

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Opinions differ as to whether RNA world constituted the first autonomous self-replicating system or was a derivative of a still-earlier system.

One version of the hypothesis is that a different type of nucleic acid, termed pre-RNA world, was the first one to emerge as a self-reproducing molecule, to be replaced by RNA world only later.

RNA world is a very similar molecule to DNA, with only two major chemical differences .

However, RNA world is less stable, being more prone to hydrolysis due to the presence of a hydroxyl group at the ribose 2' position.

RNA world uses a different set of bases than DNA—adenine, guanine, cytosine and uracil, instead of adenine, guanine, cytosine and thymine.

RNA world is thought to have preceded DNA, because of their ordering in the biosynthetic pathways.

Chemical properties of RNA world make large RNA world molecules inherently fragile, and they can easily be broken down into their constituent nucleotides through hydrolysis.

RNA world hypothesis is supported by RNA's ability both to store, transmit, and duplicate genetic information, as DNA does, and to perform enzymatic reactions, like protein-based enzymes.

In 2017, research using a numerical model suggested that a RNA world may have emerged in warm ponds on the early Earth, and that meteorites were a plausible and probable source of the RNA building blocks to these environments.

RNA world is made of long stretches of specific nucleotides arranged so that their sequence of bases carries information.

The RNA world hypothesis holds that in the primordial soup, there existed free-floating nucleotides.

One of the challenges posed by the RNA world hypothesis is to discover the pathway by which an RNA-based system transitioned to one based on DNA.

Additional evidence supporting the concept of an RNA world has resulted from research on viroids, the first representatives of a novel domain of "subviral pathogens".

Characteristics of viroids highlighted as consistent with an RNA world were their small size, high guanine and cytosine content, circular structure, structural periodicity, the lack of protein-coding ability and, in some cases, ribozyme-mediated replication.

One aspect critics of the hypothesis have focused on is that the exclusive hosts of all known viroids, angiosperms, did not evolve until billions of years after the RNA world was replaced, making viroids more likely to have arisen through later evolutionary mechanisms unrelated to the RNA world than to have survived via a cryptic host over that extended period.

Influenza virus, whose genome consists of 8 physically separated single-stranded RNA world segments, is an example of this type of virus.

RNA world believes the last universal common ancestor was RNA-based and evolved RNA viruses.

An alternative—or complementary—theory of RNA origin is proposed in the PAH world hypothesis, whereby polycyclic aromatic hydrocarbons mediate the synthesis of RNA molecules.

Iron-sulfur RNA world theory proposes that simple metabolic processes developed before genetic materials did, and these energy-producing cycles catalyzed the production of genes.

Panspermia does not invalidate the concept of an RNA world, but posits that this world or its precursors originated not on Earth but rather another, probably older, planet.

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For most of the time that followed Franklin, Watson and Crick's elucidation of DNA structure in 1953, life was largely defined in terms of DNA and proteins: DNA and proteins seemed the dominant macromolecules in the living cell, with RNA world only aiding in creating proteins from the DNA blueprint.

The RNA world hypothesis is supported by the observations that ribosomes are ribozymes: the catalytic site is composed of RNA, and proteins hold no major structural role and are of peripheral functional importance.

Likewise, in eukaryotes the maintenance of telomeres involves copying of an RNA world template that is a constituent part of the telomerase ribonucleoprotein enzyme.