Biology Reference
In-Depth Information
complementary - polymers create two new 'operational subsystems': one in
charge of the reliable recording, storage, and replication of certain sequences
(which are crucial for the correct functioning of the system and that of similar
systems in future generations) and the other strictly in charge of carrying out -
with increasing efficiency - these metabolic tasks required for the continuous
realization of the individual autonomous system (mainly contributing to the gen-
eration of more and more sophisticated mechanisms of catalysis). Then, these
former template-catalytic components (RNA) can be substituted by two others:
pure templates now completely free of any catalytic task will become tools
for an unlimited memory (as we know them in present-day DNA), and pure
catalysts, optimally suited for translating sequential variations into 3D diversity
(as happens in present-day proteins).
It must be stressed at this point that the emergence of these two new types of
processes cannot occur but from a common metabolic platform (i.e., from the
characteristic organization of the previous stage), which now becomes respon-
sible for keeping a constant bond between the two, and enables their comple-
mentary development as generations flow. Now, as these two new types of
macromolecular components (the new templates and the new catalysts) cannot
be made of the same kind of monomers or the same kind of chain bonds, an
indirect, mediated connection turns to be a requisite in order to achieve an
effective functioning between the two operational levels of the system. Thus,
the connection becomes a mechanism of a contingent nature (which does not
mean that it will be established randomly or free from any constraint). This
mechanism, known as the genetic code, is what underlies the duality between
genotype and phenotype.
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The scenario that this transition brings about is a new form of organization
based on two quite different - but complementary - forms of operation: one
involved in the fundamental productive-metabolic processes (i.e., dynamic, rate-
dependent processes) and the other (constituted by the genetic processes), partly
decoupled from all that muddle of on-line chemical reactions, puts together a
group of special processes and components (rate-independent processes), with
particular rules of composition and functioning (Pattee, 1977). Now, despite
their dynamical decoupling, both forms of operation in the system are so deeply
linked that none of them can work without the other, and therefore, the whole
system depends on their causal connection. However, as the genetic strings are
dynamically decoupled from the metabolic processes, their causal action is of a
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The genetic code, rather than a mechanism, is in fact the expression of an organization, which Pattee (1982)
has called Semantic Closure. The basic idea is that gene strings are self-interpreting symbols because their
action - specific but arbitrary as it is mediated by the recognition of certain functional components - is
the synthesis of those components (tRNAs and synthetases) that allow the causal action of the very genes.
Thus, by contributing to the maintenance of the whole cellular organization, genes in fact achieve their own
interpretation.
