Accident, frozen

Ken Schaffner So the genes moved relatively freely. What are the implications for looking for sorts of common mechanisms I could see it going either way. If the genes are moving freely and these are selected because they are very successful in the organisms which incorporate them, then you may have a rather small number of frozen accidents which are found all over the tree of life, of the bush of life. 

Clearly this means a complete rejection of the fundamental Darwinian principle of common descent. Also, he rejects mutation and natural selection as the mechanisms that produced species. Is this view also contrary to the universality of biochemistry, and in particular the monophyletic origin of life, to which most biochemists today would subscribe Probably yes but of course if one assumes an absolute determinism, then the laws of chemistry and physics would produce the same products at each different start. This goes against the notion of frozen accident and the unique origin of the genetic code. So, there was never a time on Earth with only one kind of species, and the development of species was parallel rather than sequential. Of course all these ideas are substantiated by arguments and data - for these, the reader should refer to the original sources. 

The notion of frozen accident is often used in the literature in this connection. The term conveys the idea that something which is not thermodynamically stable may have formed by accident - and then been codified somehow in the living processes. Of course it is difficult to describe specific frozen accidents in terms of actual chemistry mechanisms. The notion of a frozen accident is a pictorial and fascinating metaphor, but it does not teach us anything from the operative point of view. 

Whatever the outcome one can be sure that a physical contact type selection has led to the genomic code. Not only does the new hypothesis predict such contact, the status of evolution as a discipline of science depends upon it. Frozen accidents are not the stuff of hypotheses but more likely failures of insight. This means that the principle of code development is discoverable and with it, slowly to be sure, the whole mechanism of biochemical evolution. 

The genetic code from frozen accident to predictable adaptation... 

The theory of frozen accident assumes a chance mechanism for its origin. 

The universal genetic code has been viewed from the time of its discovery 50 years ago as a frozen accident. Some organelle genomes show a deviation from this universal code. Do these genomes provide evidence for this view of the code ... 

Biologists prefer to see in language of organismal genes and proteins the frozen accidents for which every small change affects their life (structure, function and metabolism). 

The genetic code, regardless of whether it is a product of a "frozen accident" [1] or a deterministic interaction between the nucleotides and the amino acids [2], displays an apparent correlation between the nucleotides found at particular codon positions and the physico-chemical properties of the protein amino acid residues encoded by the nucleotides [2-10]. A variety of analytical methods have been employed to quantitatively examine these relationships. SjdstrOm and Wold [5], for example, have used Principal Component Analysis (PCA) to relate twenty physical properties of the amino acids to the genetic code. They find that 58% of the variance in the data can be accounted for by considering just three factors. In order of importance, the predominant contributions are 1) hydrophobicity, 2) molar volume, and 3) electronic descriptors (e.g. pKgS and NMR chemical shifts). Fig. 1 presents a concise display of... 

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