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319 lines
25 KiB
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<title>The Gradual Evolution of RNA</title>
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<meta name="author" content="Amr Gharbeia">
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<body lang="en-GB" text="#99ccff" dir="ltr">
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<p lang="en-US" align="left" style="margin-left: 1.27cm; margin-right: 2.54cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
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<font color="#000000"><font face="Times New Roman, serif"><font size="3" style="font-size: 12pt"><font color="#993366"><font face="Verdana, sans-serif"><b>T<img src="data:image/png;base64,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" name="TtsOtkCRS01_08" align="right" hspace="5" width="150" height="63" border="0">he
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Gradual Evolution of RNA.</b></font></font> We assume, therefore,
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that RNA molecules were the original proto-organisms. But the
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original RNA molecules must have been simple, with only a few
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varieties, and barely able to go through reproductive cycles at all.
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Reproductive causation would, however, make them more complex, more
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diverse and better able to control the conditions affecting their
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reproduction. The major accomplishment of this first stage of gradual
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evolution is a much more efficient and reliable way synthesizing
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protein molecule, which helps make the second stage possible. But at
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this first stage, when the proto-organisms are so simple, there is a
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way that reproductive causation works on them at two levels of
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part-whole complexity. </font></font></font>
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</p>
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<p lang="en-US" align="left" style="margin-left: 1.27cm; margin-right: 2.54cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
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<font color="#000000"><font face="Times New Roman, serif"><font size="3" style="font-size: 12pt"><font face="Verdana, sans-serif">N<img src="data:image/png;base64,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" name="TtsOtkCRS01_09" align="right" hspace="5" width="275" height="21" border="0">atural
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selection at the individual level. </font>At the level of individual
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RNA molecules, reproductive causation leads us to expect that every
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new power to control relevant conditions would evolve as it becomes
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possible, that is, as random variations on extant RNA synthesize
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proteins happen to control some new condition that affects
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reproduction or controls some old condition better. </font></font></font>
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</p>
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<p lang="en-US" align="left" style="margin-left: 2.54cm; margin-right: 1.27cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
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<font color="#000000"><font face="Times New Roman, serif"><font size="3" style="font-size: 12pt">Those
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RNA molecules whose proteins controlled some relevant condition, such
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as supplying nucleotides for reproduction, would be more likely to
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reproduce, because they would be more likely to be located where RNA
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were benefiting from them. There would be random variations on them,
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because RNA reproduction is far from perfect. Kinds of nucleotides
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would be substituted, new nucleotides would be added, and whole RNA
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could be spliced together. Such random variations on existing RNA
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would sometimes alter the kind of amino acid used at some point in
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the protein or add new amino acids, and if these slightly different
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proteins or slightly more complex proteins were any better able to
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control the relevant condition, the RNA molecule producing them would
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be located where it was somewhat more likely to benefit from them
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and, thus, would be more likely to succeed in reproduction. </font></font></font>
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</p>
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<p lang="en-US" align="left" style="margin-left: 2.54cm; margin-right: 1.27cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
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<font color="#000000"><font face="Times New Roman, serif"><font size="3" style="font-size: 12pt">Since
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the triplets of nucleotides are the structural causes bundled
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together as a proto-organism, the relevant condition that is
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controlled by the work each does is determining which amino acid is
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appended in the growing peptide chain at some point. Different
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triplets of nucleotides in the RNA would control different relevant
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conditions by determining amino acids at other points in the protein
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being synthesized. Thus, reproductive causation would make these
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proto-organisms gradually more powerful over their whole reproductive
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cycles by altering the bundle of structural causes — shaping each
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structural cause to be as effective as possible in determining some
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amino acid, adding new structural causes when the amino acid they add
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makes the chain more power, and fitting those structural causes
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together harmoniously as parts of a single RNA — so that the RNA
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molecule eventually has maximum power over the whole cycle. But
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maximum holistic power for an RNA molecule is just whatever power
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comes from the kind of protein it produces existing in the
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neighborhood. </font></font></font>
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</p>
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<p lang="en-US" align="left" style="margin-left: 2.54cm; margin-right: 1.27cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
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<font color="#000000"><font face="Times New Roman, serif"><font size="3" style="font-size: 12pt">Even
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if evolution began with a single variety of RNA whose protein did
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some useful work, evolutionary change would not stop at making its
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protein as powerful as possible, because some random variations on
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existing RNA would synthesize proteins that controlled other relevant
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conditions. If the first kind of protein supplied nucleotides for RNA
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synthesis, there are surely random variations on its RNA template
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whose slightly different protein molecules would supply other kinds
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of nucleotides, or supply the same kinds of nucleotides in from other
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sources. Again, random variations on existing RNA that happened to
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control some new condition affecting RNA reproduction would be more
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likely to succeed in reproducing, because their location in the
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region would make the more likely to benefit. Thus, from the original
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RNA molecule(s) would evolve a variety of RNA molecules serving as
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templates for proteins with different functions, and each would
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become maximally powerful in serving its function.</font></font></font></p>
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<p lang="en-US" align="left" style="margin-left: 1.27cm; margin-right: 2.54cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
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<font color="#000000"><font face="Times New Roman, serif"><font size="3" style="font-size: 12pt"><font face="Verdana, sans-serif">N<img src="data:image/png;base64,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" name="TtsOtkCRS01_10" align="right" hspace="5" width="275" height="23" border="0">atural
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selection at the group level.</font> The increasing diversity of RNA
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molecules would make their combination in local regions an ecology,
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and the most spectacular accomplishments of the first stage of
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evolution, such as a more efficient and reliable process of
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synthesizing proteins, would come from the increasing power of the
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ecology as a whole. </font></font></font>
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</p>
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<p lang="en-US" align="left" style="margin-left: 2.54cm; margin-right: 1.27cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
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<font color="#000000"><font face="Times New Roman, serif"><font size="3" style="font-size: 12pt">Natural
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selection would not be very selective at first. Though RNA whose
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proteins controlled some relevant conditions would be more likely to
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reproduce because they would be in the right location to benefit from
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the protein, other nearby RNA would also tend to benefit. But once
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there were enough different kinds of RNA whose proteins making
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different contributions to the reproduction of them all, change in
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the direction of maximum holistic power at the ecological level would
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be accelerated by a weak form of reproductive causation at the level
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of local ecologies. </font></font></font>
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</p>
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<p lang="en-US" align="left" style="margin-left: 2.54cm; margin-right: 1.27cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
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<font color="#000000"><font face="Times New Roman, serif"><font size="3" style="font-size: 12pt">Different
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local ecologies would be like different higher level organisms trying
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out different combinations of RNA. Each local region would contain
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various kinds of RNA, synthesizing various kinds of proteins, and
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they would all be driven through cycles of reproduction by the cycle
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of night and day side by side in the water. The varieties of RNA
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would be like the many structural causes “bundled together” like
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a higher level organism, for the proteins synthesized by all of them
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would tend to <i>jointly </i>control conditions in their local region
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that affected the reproduction of them all. And such ecologies of RNA
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molecules would also be able to reproduce as a whole, like higher
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level organisms, because when storms or other major disturbances
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scattered molecules to new local regions, and RNA that wound up in
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favorable circumstances where they could have both structural effects
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would start new colonies. Colonies with the right combinations of
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varieties of RNA would generate proteins of different kinds whose
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joint control of conditions affecting the reproductive of them all
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would make their populations of RNA grow faster. Thus, when the next
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storm came along, the more powerful combinations of RNA molecules
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would tend to populate the favorable locations when more normal
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conditions resumed. Random variations in bundling RNA together would
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be introduced by the reproduction of such “higher level organisms,”
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because the varieties of RNA that would wind up together in any given
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local region would be a mixture of varieties of RNA from several
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local regions. Since there are only so many favorable locations for
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such colonies of RNA to be set up, their reproduction would
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eventually make free energy scarce, and a natural selection would be
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made by the greater reproductive success of some whole colonies. </font></font></font>
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</p>
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<p lang="en-US" align="left" style="margin-left: 2.54cm; margin-right: 1.27cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
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<font color="#000000"><font face="Times New Roman, serif"><font size="3" style="font-size: 12pt">The
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relative lack of selectivity about natural selection at the level of
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individual RNA molecules would, therefore, make possible a powerful
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form of group selection, which would make the combination of
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different varieties of RNA in each region as powerful as possible as
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a whole in controlling all the conditions that affect RNA
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reproduction generally. Since random variations at the level of these
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higher level “ecological organisms” are made possible by how they
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are made up of RNA molecules as parts, there are three ways in which
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random variations may make them more powerful as a whole. </font></font></font>
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</p>
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<p lang="en-US" align="left" style="margin-left: 3.81cm; margin-right: 2.03cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
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<font color="#000000"><font face="Times New Roman, serif">The first
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kind of change that occurs at the higher level of part-whole
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complexity (the local regions where RNA exists side-by-side in space)
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is the gradual change in each variety of RNA that shapes its protein
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to perform its function as effectively as possible. This is the
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gradual change described at the outset of this description of the
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gradual evolution of RNA, which itself involves three kinds of change
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because each RNA molecules is a bundle of structural causes, with
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each triplet of nucleotide determining the amino acid for some
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location in its protein molecule. Random variations on the RNA
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molecule that synthesizes it would try out variations on the protein,
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and the more effective varieties would tend to be the ones that
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succeed in reproducing, because they would be located in the local
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region where the condition was controlled and so there would be more
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of them to be scattered to new regions when a storm or other
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disturbance occurred.</font></font></p>
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<p lang="en-US" align="left" style="margin-left: 3.81cm; margin-right: 2.03cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
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<font color="#000000"><font face="Times New Roman, serif">Second, new
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varieties of RNA would be added to the colony when random variations
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on existing RNA happen to synthesize a protein that controls some new
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condition that affects their reproduction (or some old condition in a
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new way). Not only would it tend to be selected within the colony by
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its greater likelihood of being located where the protein’s benefit
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was provided, but it would eventually be added to the mix in other
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local regions. To take an extreme example, suppose that it alleviated
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some bottleneck in the process affecting them all. That would make
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all the RNA in the local region would be more successful in
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reproducing, and there would be more RNA from that colony to scatter
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to new local regions when the next storm came.</font></font></p>
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<p lang="en-US" align="left" style="margin-left: 3.81cm; margin-right: 2.03cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
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<font color="#000000"><font face="Times New Roman, serif">Third, the
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useful proteins that were being synthesized would also be shaped to
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work together as harmoniously and efficiently as possible with other
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proteins in local regions, because the reproduction of all the RNA
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molecules in the neighborhood is the joint result of the proteins
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synthesized by all the RNA. Thus, as different combinations of RNA
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molecules were tried out in different regions, those combinations
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that worked together most harmoniously and even assisted one another
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would tend to succeed, while less harmonious combinations would fail,
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because there would be more of them to scatter to new regions when
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storms or other disturbances occurred. </font></font>
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</p>
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<p lang="en-US" align="left" style="margin-left: 1.27cm; margin-right: 2.54cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
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<font color="#000000"><font face="Times New Roman, serif"><font size="3" style="font-size: 12pt">Reproductive
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causation was still weak, but since it was operating on the level of
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whole ecologies of RNA as well as on each variety of RNA within a
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local region, there would be an increase in the power of whole
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colonies of RNA to control conditions that affect the reproduction of
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them all. Although RNA molecules start off simple, weak and uniform,
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their stage of gradual evolution would eventually make them complex,
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powerful and diverse. Indeed, this would happen to whole colonies of
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RNA, because insofar as there is a range of different favorable
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locations for them, different combinations of RNA would evolve to tap
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the free energy available in all of them. The surface of a planet
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surely makes it possible for RNA molecules to go through reproductive
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cycles on a sufficiently large scale to try out all the random
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variations on existing RNA that are possible, and thus, each new
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relevant condition that could be controlled would be brought under
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control as it became possible. </font></font></font>
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</p>
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<p lang="en-US" align="left" style="margin-left: 1.27cm; margin-right: 2.54cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
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<font color="#000000"><font face="Times New Roman, serif"><font size="3" style="font-size: 12pt"><font face="Verdana, sans-serif">M<img src="data:image/png;base64,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" name="TtsOtkCRS01_11" align="right" hspace="5" width="275" height="21" border="0">ore
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efficient and reliable protein synthesis.</font> It is not necessary
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to trace the whole course of the gradual evolution of RNA, but it is
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worth mentioning what is probably its most significant contribution
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to subsequent evolution, namely, an efficient and reliable way of
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synthesizing protein molecules. </font></font></font>
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</p>
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<p lang="en-US" align="left" style="margin-left: 2.54cm; margin-right: 1.27cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
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<font color="#000000"><font face="Times New Roman, serif"><font size="3" style="font-size: 12pt">The
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original process by which RNA molecules synthesized the proteins that
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brought the first relevant conditions under control (such as
|
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supplying energy-rich parts for RNA replication) was probably weak
|
||
and inefficient. The power to control relevant conditions of all
|
||
kinds would have been greatly increased, therefore, by random
|
||
variations whose proteins made the synthesis of proteins more
|
||
reliable or powerful. There are many ways it could have been
|
||
improved, including changes that expanded the kinds of amino acids
|
||
that could be used. The first improvements may have been proteins
|
||
that helped line up amino acids with the RNA and a substratum so that
|
||
the protein chain was more likely to form. Such changes could have
|
||
had far reaching effects, because it could give a function to
|
||
previously useless proteins that were relatively abundant because
|
||
they were so simple that they were continually being tried out,
|
||
eventually selecting the RNA molecules that synthesized them. But the
|
||
nature of the primitive means of protein synthesis is obscure, and
|
||
the reason could be that major changes occurred its early evolution.</font></font></font></p>
|
||
<p lang="en-US" align="left" style="margin-left: 3.81cm; margin-right: 2.03cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
|
||
<font color="#000000"><font face="Times New Roman, serif">One
|
||
indication that the original way of having a structural effect in
|
||
addition to reproduction involved the synthesis of amino acids is
|
||
that the successive bases, which are the information-carrying face of
|
||
nucleotides, can be held together in chains by amino acids as well as
|
||
by the phosphates used in RNA (and DNA). Such chains of amino acids
|
||
are called "peptides," the chain that carries these bases
|
||
are called PNA (rtaher than RNA or DNA). It means that amino acids
|
||
interact with the molecules by which nucleotides determine which kind
|
||
of amino acid to attach next in a way that could have occurred
|
||
without the elaborate molecular machinery now used. </font></font>
|
||
</p>
|
||
<p lang="en-US" align="left" style="margin-left: 2.54cm; margin-right: 1.27cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
|
||
<font color="#000000"><font face="Times New Roman, serif"><font size="3" style="font-size: 12pt">An
|
||
example of a major evolutionary change would be the addition or
|
||
deletion of the kinds of nucleic acids used. Protein synthesis may
|
||
originally have involved only two or three nucleic acids and others
|
||
were added as special proteins evolved that enabled them to use new
|
||
kinds of amino acids in the proteins being synthesized. Or it may
|
||
originally have used kinds of nucleic acids that interact more
|
||
readily with amino acids and they subsequently dropped out when
|
||
proteins evolved that enabled fewer nucleic acids to determine the
|
||
amino acid to be added. It may even be possible that the original
|
||
code used only two nucleic acids to identify which of the amino acids
|
||
then being used were to be added, and later, assisted by new
|
||
proteins, it was replaced by the three-nucleotide code found in
|
||
existing living objects. But whatever the major changes were that
|
||
occurred early in its evolution, they not only made it possible for
|
||
RNA molecules to do their work more reliably and efficiently, but
|
||
probably also increased the variety of amino acids used in
|
||
constructing proteins from the few kinds that were probably involved
|
||
at first to the twenty or so kinds of amino acids found in living
|
||
objects. </font></font></font>
|
||
</p>
|
||
<p lang="en-US" align="left" style="margin-left: 3.81cm; margin-right: 2.03cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
|
||
<font color="#000000"><font face="Times New Roman, serif">Only 20 or
|
||
so kinds of amino acids are used in synthesizing proteins, but they
|
||
were selected from the enormous variety of amino acids that was
|
||
availabe at the time. What singled these amino acids out was
|
||
presumably that they provided enough variety for sequences of them to
|
||
serve as all the kinds of molecular machines needed to handle other
|
||
molecules. There is probably a geometrical aspect to the amino acids
|
||
used that enables them to be combined in all the basic ways required
|
||
to construct complex structural causes, and when it is explained, the
|
||
currently intractable problem of predicing the conformations of
|
||
proteins from their amino-acid sequence will have largely been
|
||
solved. </font></font>
|
||
</p>
|
||
<p lang="en-US" align="left" style="margin-left: 2.54cm; margin-right: 1.27cm; text-indent: 0cm; margin-top: 0.49cm; margin-bottom: 0.49cm; line-height: 100%; widows: 0; orphans: 0">
|
||
<font color="#000000"><font face="Times New Roman, serif"><font size="3" style="font-size: 12pt">Though
|
||
the addition of new proteins to assist the process of protein
|
||
synthesis would make such major changes possible, they would, at the
|
||
same time, make the link between the nucleotides and amino acids more
|
||
indirect. That would explain how the primitive way of synthesizing
|
||
proteins evolved into its current, complex form. Even in the simplest
|
||
forms of life on earth, protein synthesis depends on the interaction
|
||
of RNA molecules with a complex machine composed of as many as
|
||
fifty-five different protein molecules and three RNA molecules.
|
||
"Ribosomes", as they are called, assemble themselves
|
||
automatically in water because of their geometrical structures and
|
||
how weak forces located on them bind them together. And they can
|
||
consume only amino acids that have been attached as parts of tRNA
|
||
molecules. But little is known about how ribosomes works, and when it
|
||
is worked lut, there may well be empirical proof that original way in
|
||
which RNA structural effects for doing non-reproductive work was a
|
||
direct interaction between RNA and amino acids that linked them
|
||
together in short chains.</font></font></font></p>
|
||
</body>
|
||
</html>
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