Enoch2021 wrote:
Danmark wrote:
"
RNA synthesis and replication
The RNA world has spurred scientists to try to determine if RNA molecules could have spontaneously formed that were capable of catalyzing their own replication.[129][130][131] Evidences suggest chemical conditions (including the presence of boron, molybdenum and oxygen) for initially producing RNA molecules may have been better on the planet Mars than those on the planet Earth.[129][130] If so, life-suitable molecules, originating on Mars, may have later migrated to Earth via meteor ejections.[129][130]
A number of hypotheses of modes of formation have been put forward. As of 1994, there were difficulties in the abiotic synthesis of the nucleotides cytosine and uracil.[132] Subsequent research has shown possible routes of synthesis; for example, formamide produces all four ribonucleotides and other biological molecules when warmed in the presence of various terrestrial minerals.[87][88] Early cell membranes could have formed spontaneously from proteinoids, which are protein-like molecules produced when amino acid solutions are heated while in the correct concentration in aqueous solution. These are seen to form micro-spheres which are observed to behave similarly to membrane-enclosed compartments. Other possibilities include systems of chemical reactions that take place within clay substrates or on the surface of pyrite rocks.
Factors supportive of an important role for RNA in early life include its ability to act both to store information and to catalyze chemical reactions (as a ribozyme); its many important roles as an intermediate in the expression and maintenance of the genetic information (in the form of DNA) in modern organisms; and the ease of chemical synthesis of at least the components of the molecule under the conditions that approximated the early Earth.
Relatively short RNA molecules have been artificially produced in labs, which are capable of replication.[133] Such replicase RNA, which functions as both code and catalyst provides its own template upon which copying can occur. Jack Szostak has shown that
certain catalytic RNAs can, indeed, join smaller RNA sequences together, creating the potential, in the right conditions for self-replication. If these conditions were present, Darwinian selection would favour the proliferation of such autocatalytic sets, to which further functionalities could be added.[134] Lincoln and Joyce have identified such autocatalytic systems of RNA capable of self-sustained replication.[135] The systems, which include two ribozymes that catalyze each other's synthesis, replicated with doubling time of about one hour, and were subject to natural selection.[136] In evolutionary competition experiments, this led to the emergence of new systems which replicated more efficiently.[122] This was the first demonstration of evolutionary adaptation occurring in a molecular genetic system.[136]"
http://en.wikipedia.org/wiki/Abiogenesi ... eplication
A "wiki" source? Oh My, sir
If that is shorthand for "I don't believe anything on Wikipedia," I suggest you read the footnotes provided. There were 259 listed at that URL
Regarding RNA you could start with:
Copley, SD; Smith, E; Morowitz, HJ (2007). "The origin of the RNA world: co-evolution of genes and metabolism.". Bioorg Chem 35 (6): 430"43. doi:10.1016/j.bioorg.2007.08.001. PMID 17897696. "The proposal that life on Earth arose from an RNA World is widely accepted."
Orgel, LE (2003). "Some consequences of the RNA world hypothesis". Orig Life Evol Biosph 33 (2): 211"8. PMID 12967268. "It now seems very likely that our familiar DNA/RNA/protein world was preceded by an RNA world"
Robertson, MP; Joyce, GF (2012). "The origins of the RNA world". Cold Spring Harb Perspect Biol 4 (5). doi:10.1101/cshperspect.a003608. PMC 3331698. PMID 20739415. "There is now strong evidence indicating that an RNA World did indeed exist before DNA- and protein-based life."
Neveu, M; Kim, HJ; Benner, SA (2013). "The "strong" RNA world hypothesis: fifty years old". Astrobiology 13 (4): 391"403. doi:10.1089/ast.2012.0868. PMID 23551238."[The RNA world's existence] has broad support within the community today."
^ Jump up to: a b c Robertson, MP; Joyce, GF (2012). "The origins of the RNA world". Cold Spring Harb Perspect Biol 4 (5). doi:10.1101/cshperspect.a003608. PMC 3331698. PMID 20739415.
^ Jump up to: a b c Cech, TR (2012). "The RNA worlds in context.". Cold Spring Harb Perspect Biol 4 (7): a006742. doi:10.1101/cshperspect.a006742. PMC 3385955. PMID 21441585.
Jump up ^ Yarus, M (2011). "Getting past the RNA world: the initial Darwinian ancestor". Cold Spring Harb Perspect Biol 3 (4). doi:10.1101/cshperspect.a003590. PMC 3062219. PMID 20719875.
Jump up ^ Neveu, M; Kim, HJ; Benner, SA (2013). "The "strong" RNA world hypothesis: fifty years old". Astrobiology 13 (4): 391"403. doi:10.1089/ast.2012.0868. PMID 23551238.
Jump up ^ Gilbert, Walter (20 February 1986). "Origin of life: The RNA world". Nature 319 (6055): 618"618. Bibcode:1986Natur.319..618G. doi:10.1038/319618a0.
Jump up ^ Noller, HF (2012). "Evolution of protein synthesis from an RNA world.". Cold Spring Harb Perspect Biol 4 (4): a003681. doi:10.1101/cshperspect.a003681. PMC 3312679. PMID 20610545.
^ Jump up to: a b Koonin, Eugene V. (31 May 2007). "The cosmological model of eternal inflation and the transition from chance to biological evolution in the history of life". Biol. Direct (2). p. 15. doi:10.1186/1745-6150-2-15. PMC 1892545.
^ Jump up to: a b c Zimmer, Carl (12 September 2013). "A Far-Flung Possibility for the Origin of Life". New York Times.
^ Jump up to: a b c Webb, Richard (29 August 2013). "Primordial broth of life was a dry Martian cup-a-soup". New Scientist.
Jump up ^ Ma, W; Yu, C; Zhang, W; Hu, J (November 2007). "Nucleotide synthetase ribozymes may have emerged first in the RNA world". RNA 13 (11): 2012"9. doi:10.1261/rna.658507. PMC 2040096. PMID 17878321.
Orgel, L. (1994). "The origin of life on Earth". Scientific American 271 (4): 81. doi:10.1038/scientificamerican1094-76. PMID 7524147.
Jump up ^ Johnston, W. K. et al. (2001). "RNA-Catalyzed RNA Polymerization: Accurate and General RNA-Templated Primer Extension". Science 292 (5520): 1319"25. Bibcode:2001Sci...292.1319J. doi:10.1126/science.1060786. PMID 11358999.
Jump up ^ Szostak, Jack W. (4 June 2008). "The Origins of Function in Biological Nucleic Acids, Proteins, and Membranes". HHMI.
Jump up ^ Lincoln, Tracey A.; Joyce, Gerald F. (8 January 2009). "Self-Sustained Replication of an RNA Enzyme". Science 323 (5918): 1229"32. Bibcode:2009Sci...323.1229L. doi:10.1126/science.1167856. PMC 2652413. PMID 19131595.
^ Jump up to: a b Joyce, GF (2009). "Evolution in an RNA world.". Cold Spring Harb Symp Quant Biol 74: 17"23. doi:10.1101/sqb.2009.74.004. PMC 2891321. PMID 19667013.
Here's a free abstract of just the first source provided:
Abstract
Discoveries demonstrating that RNA can serve genetic, catalytic, structural, and regulatory roles have provided strong support for the existence of an RNA World that preceded the origin of life as we know it. Despite the appeal of this idea, it has been difficult to explain how macromolecular RNAs emerged from small molecules available on the early Earth. We propose here a mechanism by which mutual catalysis in a pre-biotic network initiated a progression of stages characterized by ever larger and more effective catalysts supporting a proto-metabolic network, and the emergence of RNA as the dominant macromolecule due to its ability to both catalyze chemical reactions and to be copied in a template-directed manner. This model suggests that many features of modern life, including the biosynthetic pathways leading to simple metabolites, the structures of organic and metal ion cofactors, homochirality, and template-directed replication of nucleic acids, arose long before the RNA World and were retained as pre-biotic systems became more sophisticated.
