Uma teoria geral de design biológico?

Na conclusão do artigo abaixo Koonin e Novozhilov, disseram:

“... é possível que qualquer cenário da origem e evolução do código [genético] permanecerá vazio se não for combinado com a compreensão da origem do próprio princípio de codificação e o sistema de tradução que isso caracteriza. No âmago deste problema, está um círculo vicioso enfadonho: qual teria sido a força seletiva por detrás da evolução do sistema de tradução extremamente complexo antes que existissem proteínas funcionais? E, é claro, não existiriam proteínas sem um sistema de tradução suficientemente efetivo. Uma variedade de hipóteses tem sido proposta em tentativas de se quebrar o círculo, mas até agora nenhuma delas parece ser suficientemente coerente ou goze de apoio suficiente para afirmar o status de uma verdadeira teoria.” [1]

“Portais de complexidade” que são verdadeiros, i.e., passíveis de serem descobertos, poderiam fornecer a base de uma teoria geral de design biológico, pois no parágrafo 5 deste artigo Koonin e Novozhilov descrevem “o portal de complexidade que é exigido para produzir proteínas funcionais” [2]

Koonin e Novozhilov são evolucionistas, e até onde eu sei, não são adeptos da teoria do Design Inteligente, mas estão elaborando aqui sobre “complexidade irredutível” e origem da informação genética. Não parecem teóricos do DI publicando suas teses em publicações científicas com revisão por pares?

Portais de complexidade? Eu acho que nós estamos à beira de uma teoria geral de design biológico.

Quem viver, verá!

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IUBMB Life. 2008 Dec 31.

Koonin EV, Novozhilov AS.

“Origin and evolution of the genetic code: The universal enigma,” by Eugene V. Koonin and Artem S. Novozhilov, forthcoming in IUBMB Life, published online 31 Dec 2008.
National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA.
The genetic code is nearly universal, and the arrangement of the codons in the standard codon table is highly nonrandom. The three main concepts on the origin and evolution of the code are the stereochemical theory, according to which codon assignments are dictated by physicochemical affinity between amino acids and the cognate codons (anticodons); the coevolution theory, which posits that the code structure coevolved with amino acid biosynthesis pathways; and the error minimization theory under which selection to minimize the adverse effect of point mutations and translation errors was the principal factor of the code's evolution. These theories are not mutually exclusive and are also compatible with the frozen accident hypothesis, that is, the notion that the standard code might have no special properties but was fixed simply because all extant life forms share a common ancestor, with subsequent changes to the code, mostly, precluded by the deleterious effect of codon reassignment. Mathematical analysis of the structure and possible evolutionary trajectories of the code shows that it is highly robust to translational misreading but there are numerous more robust codes, so the standard code potentially could evolve from a random code via a short sequence of codon series reassignments. Thus, much of the evolution that led to the standard code could be a combination of frozen accident with selection for error minimization although contributions from coevolution of the code with metabolic pathways and weak affinities between amino acids and nucleotide triplets cannot be ruled out. However, such scenarios for the code evolution are based on formal schemes whose relevance to the actual primordial evolution is uncertain. A real understanding of the code origin and evolution is likely to be attainable only in conjunction with a credible scenario for the evolution of the coding principle itself and the translation system. (c)
2008 IUBMB Life, 2008.
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NOTAS

1. “...it stands to reason that any scenario of the code origin and evolution will remain vacuous if not combined with understanding of the origin of the coding principle itself and the translation system that embodies it. At the heart of this problem, is a dreary vicious circle: what would be the selective force behind the evolution of the extremely complex translation system before there were functional proteins? And, of course, there could be no proteins without a sufficiently effective translation system. A variety of hypotheses have been proposed in attempts to break the circle, but so far none of these seems to be sufficiently coherent or enjoys sufficient support to claim the status of a real theory.”

2. “the complexity threshold that is required to yield functional proteins”

As notas acima não correspondem às do artigo a ser publicado.