3 ms·

>and also an earlier stage, when only RNA replication existed, but RNA did not perform any useful function for its host living being, but it was only a virus th

>and also an earlier stage, when only RNA replication existed, but RNA did not perform any useful function for its host living being, but it was only a virus that was replicated using energy and molecular components from its host. And in this stage, where there is no DNA, what molecule carried the genetic information of these host organisms? >Because any memory molecule, like RNA, needs an already existing living being for its first replication No, it doesn't. RNA is capable of folding into complex catalytic machineries same as polypeptide chains (aka. proteins). An RNA synthetase itself composed of RNA is absolutely probable.

adrian_b 5y ago
As I have already said, there is no need for genetic information in a living being able to grow and reproduce. The difference between a living being with genetic information and a living being without genetic information is the same as between a processor with micro-programmed control and a processor with hard-wired control. In a processor with micro-programmed control, it is easy to add new instructions or to replace the instructions that it can execute with others having a completely different behavior, just by changing the content of the control memory. In a processor with hard-wired control, you might be able to change the interconnections between blocks or to replace some logical gates with other kinds of logical gates, but the chances that these changes will result in a new processor that will still function and do something useful are minuscule. Genetic information is necessary for the evolution of simple self-reproducing living beings to the complex living beings that exist today, but it is not necessary for life, i.e. for growth and reproduction of complex molecules. It is fortunate that this is true, because otherwise there would have not been any path from inanimate matter to memory molecules like RNA, because they cannot continue to exist without being replicated from the template of an already existing memory molecule, so they cannot have any other function earlier than the first replication begins to produce them, and the replication cannot appear before the monomers, e.g. ATP, are available. About the RNA synthetase, that is just a catalyst. It cannot produce any RNA without the monomers (nucleotides) and without energy, i.e. a dehydrating agent like ATP, which must extract the water from the monomers, to condense them in the RNA polymer. In the first living beings that used ATP and the other nucleotides to perform condensation reactions, the reactions were not controlled as well as today, so there were many parasite reactions that consumed a part of the reactants instead of producing the desirable end products. So some of the ATP molecules must have condensed with themselves and with other nucleotides, instead of producing useful polymers. From these ATP condensation side-reactions, some kind of RNA synthetase must have been produced by chance and then it began to replicate itself. However that was possible only because ATP and nucleotides produced continuously by the host metabolism were available. Without monomers, the RNA synthetase would not have been able to do anything.
- usrbinbash 5y ago
  >there is no need for genetic information in a living being able to grow and reproduce. Yes there is, because one of the principles that define life is the ability to "pass traits onto offspring". This isn't possible without a medium to carry that information. Self replicating systems do not require information. Self replicating systems that are "alive" by any definiton in the scientific literature, do. >It cannot produce any RNA without the monomers (nucleotides) and without energy, i.e. a dehydrating agent like ATP In the same way RNA folds could catalyse RNA synthesis, other folding patterns could break down energy-rich compounds and generate nucleotides. The one thing they need for this to work, is an enclosed reaction environment, aka a lipid-vesicle, which form spotaneously as long as there are fatty acids. So no, the RNA world does NOT require some form of non-genetic-host-organisms. Folded RNA molecules within lipid vesicles are likely the earliest form of organised life.
- deleted 5y ago
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adrian_b 5y ago

As I have already said, there is no need for genetic information in a living being able to grow and reproduce. The difference between a living being with genetic information and a living being without genetic information is the same as between a processor with micro-programmed control and a processor with hard-wired control. In a processor with micro-programmed control, it is easy to add new instructions or to replace the instructions that it can execute with others having a completely different behavior, just by changing the content of the control memory. In a processor with hard-wired control, you might be able to change the interconnections between blocks or to replace some logical gates with other kinds of logical gates, but the chances that these changes will result in a new processor that will still function and do something useful are minuscule. Genetic information is necessary for the evolution of simple self-reproducing living beings to the complex living beings that exist today, but it is not necessary for life, i.e. for growth and reproduction of complex molecules. It is fortunate that this is true, because otherwise there would have not been any path from inanimate matter to memory molecules like RNA, because they cannot continue to exist without being replicated from the template of an already existing memory molecule, so they cannot have any other function earlier than the first replication begins to produce them, and the replication cannot appear before the monomers, e.g. ATP, are available. About the RNA synthetase, that is just a catalyst. It cannot produce any RNA without the monomers (nucleotides) and without energy, i.e. a dehydrating agent like ATP, which must extract the water from the monomers, to condense them in the RNA polymer. In the first living beings that used ATP and the other nucleotides to perform condensation reactions, the reactions were not controlled as well as today, so there were many parasite reactions that consumed a part of the reactants instead of producing the desirable end products. So some of the ATP molecules must have condensed with themselves and with other nucleotides, instead of producing useful polymers. From these ATP condensation side-reactions, some kind of RNA synthetase must have been produced by chance and then it began to replicate itself. However that was possible only because ATP and nucleotides produced continuously by the host metabolism were available. Without monomers, the RNA synthetase would not have been able to do anything.

usrbinbash 5y ago
>there is no need for genetic information in a living being able to grow and reproduce. Yes there is, because one of the principles that define life is the ability to "pass traits onto offspring". This isn't possible without a medium to carry that information. Self replicating systems do not require information. Self replicating systems that are "alive" by any definiton in the scientific literature, do. >It cannot produce any RNA without the monomers (nucleotides) and without energy, i.e. a dehydrating agent like ATP In the same way RNA folds could catalyse RNA synthesis, other folding patterns could break down energy-rich compounds and generate nucleotides. The one thing they need for this to work, is an enclosed reaction environment, aka a lipid-vesicle, which form spotaneously as long as there are fatty acids. So no, the RNA world does NOT require some form of non-genetic-host-organisms. Folded RNA molecules within lipid vesicles are likely the earliest form of organised life.
deleted 5y ago
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