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Origin of Life:   What is Wrong with RNA World Hypothesis
 

Origin of Life: What is Wrong with RNA World Hypothesis

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Summary: RNA world hypothesis about origin of life was based on known properties of RNA but in formulating this hypothesis, limitations of RNA as a molecule capable of independently supporting life ...

Summary: RNA world hypothesis about origin of life was based on known properties of RNA but in formulating this hypothesis, limitations of RNA as a molecule capable of independently supporting life like activities were overlooked. These limitations are pointed out and DNA is suggested as the more plausible alternative.

Author: Dr Mahesh C. Jain is a practicing medical doctor and has written the book “Encounter of Science with Philosophy – A synthetic view”. The book begins with first chapter devoted to scientifically valid concept of God and then explains cosmic phenomena right from origin of nature and universe up to origin of life and evolution of man. The book includes several chapters devoted to auxiliary concepts and social sciences as corollaries to the concept of God. This is the only book which deals with origin of nature and universe from null. Twenty-ninth chapter of the book deals with the subject matter of ‘Origin of Life’.

http://www.sciencengod.com

http://curatio.in


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    Origin of Life:   What is Wrong with RNA World Hypothesis Origin of Life: What is Wrong with RNA World Hypothesis Document Transcript

    • Origin of Life: What is Wrong with RNA World HypothesisSummary: RNA world hypothesis about origin of life was based on knownproperties of RNA but in formulating this hypothesis, limitations of RNA as amolecule capable of independently supporting life like activities were overlooked.These limitations are pointed out and DNA is suggested as the more plausiblealternative.The phrase "RNA World" was first used by Nobel laureate Walter Gilbert in 1986,in a commentary on recent observations of the catalytic properties of variousforms of RNA.The RNA world hypothesis is supported by RNAs ability to store, transmit, andduplicate genetic information, as DNA does. RNA can act as a ribozyme, a specialtype of enzyme. Because it can perform the tasks of both DNA and enzymes, RNAis believed to have once been capable of supporting independent life forms.Some viruses use RNA as their genetic material, rather than DNA.RNA world hypothesis is further supported by computational ability of RNA. Allthe three i.e. DNA, RNA and Peptides have been shown to possess computationalability. RNA computing has been used to find solutions to Knight Problem in chess. 1024strands were used. RNA computing correctly identified 43 out of 512 possiblesolutions with one error. Considering very high specificity of natural biochemicalreactions, error checking and correcting mechanisms must co-exist with RNAcomputing. This explains need for existence of antisense RNA but at the sametime raises doubts about ability of RNA alone to support a living system or life likeactivity.Self replicative ability of RNA is not without limitations. Only short RNA moleculeshave been shown to possess this ability and with a questionable fidelity. Oneversion, 189-bases long, had fidelity of 98.9% which would mean it would makean exact copy of an RNA molecule as long as itself in one of every eight copies.This 189 base pair ribozyme could polymerize a template of at most 14nucleotides in length, which is too short for replication. However this level ofinfidelity and limitation to self replication is far too high for living systems to bear.Just a single mutation affecting just one base pair in the entire genome is known
    • to be catastrophic, therefore the kind of self replication seen under lab conditionsdoes not support RNA world hypothesis.RNA is much more unstable then DNA. This inherent instability of RNA is a furtherlimitation to the ability of RNA to account for origin of life. Living organisms keeptheir identity and integrity over eons of time and across a vast number ofgenerations. With no provision for RNA repair mechanisms of the kind seen forDNA in living systems, RNA is inherently incapable of performing this task. Autocatalysis: Julius Rebek and his colleagues have shown that in anexperimental system containing amino acid adenosine and penta fluorophenylester with autocatalyst Amino Adenosine triacid ester variants (AATE variants)wherein a particular AATE variant autocatalysed its own synthesis. Therefore, thisexperiment demonstrates that nucleic acids were not absolute necessity for initiallife like activity. Autocatalytic, autoreplicative property may be regarded as one ofthe properties of matter. These autocatalysts can give rise to population ofentities with heredity which could exhibit mutual competition. By no stretch ofimagination the particular AATE variant can be regarded as living. Thereforepresence of autoreplicative and autocatalyzing property is insufficient to accountfor origin of life.All the properties of RNA which lend credibility to RNA world hypothesis arepresent in DNA but without the limitations of RNA. Moreover DNA unlike RNA isable to form much longer sequences and is much more stable then RNA (DNA haspropensity to spontaneous hydrolytic cleavage @1 per million base pair per daywith highly efficient DNA repair mechanisms to maintain the status quo) and thusis not only capable of keeping identity and integrity of the organism but alsocapable of supporting phenomenon of inheritance. Also only DNA is capable ofcarrying the amount of information needed to support a living system by virtue ofits ability to form long sequences of nucleotide bases.RNA world hypothesis finds some support due to existence of RNA viruses andviroids which are not dependent on DNA during their entire life cycle. Butavailable evidence indicates that these are able to survive only within eukaryoticcells which further imply that RNA can’t account for origin of life. Since lifeoriginated about 4 billion years back whereas origin of eukaryotes has beenestimated to be only 1.6 – 2.1 billion years back.
    • Moreover the lab conditions under which various experiments in support of RNAworld hypothesis have been conducted have not been shown to naturally exist.Even the nature of chemistry demonstrated in support of RNA world hypothesis isstochastic and not definitive and deterministic. Definitive and deterministicchemistry is the hall mark of biochemistry with no room for aberrant, random,side reactions.Therefore life could have originated only as a DNA molecule because DNA is theonly molecule capable of independently supporting all life like activities.Author: Dr Mahesh C. Jain is a practicing medical doctor and has written thebook “Encounter of Science with Philosophy – A synthetic view”. The book beginswith first chapter devoted to scientifically valid concept of God and then explainscosmic phenomena right from origin of nature and universe up to origin of lifeand evolution of man. The book includes several chapters devoted to auxiliaryconcepts and social sciences as corollaries to the concept of God. This is the onlybook which deals with origin of nature and universe from null. Twenty-ninthchapter of the book deals with the subject matter of ‘Origin of Life’. http://www.sciencengod.comhttp://curatio.in