The Origin of Gene Expression
Crystal structure of a reverse polymerase is a paper published by PNAS. Its authors are John J. Perona and Javin P. Oza. The first sentence reads: "The primary transcripts of transfer RNA (tRNA) molecules undergo extensive processing and chemical modification to become functional components of the protein synthesis apparatus." Transfer RNA (tRNA) plays a central role in some origin of life scenarios describing how a genetic code might have arisen in a precellular environment. Cells must translate information stored in DNA to enable protein synthesis. Codons correlating to specific amino acids need to be paired and properly sequenced so as to make possible functional sequences of polypeptides. Sets of enzymes known as tRNA synthetases ensure the attachment of a specific amino acid to a specified tRNA.
The paper alludes to modification of primary tRNA transcripts. Chemical modification makes functional specificity possible. Described is an instance of guanosine attachment to tRNA making recognition by histidyl-tRNA synthetase possible. Plausible scenarios for the evolution of gene expression modification components are possible but some degree of minimal cellular functionality is a prerequisite in the view of this writer.
That view is sometimes criticized as an argument based on personal incredulity. That's an odd critique in view of the fact that specified pathways are in acutely short supply. What's the opposite of personal incredulity? Unquestioning faith? Sounds close. If skepticism is grounded in the complexity of that which is observed and a process allowing that x, y and z can evolve depends on greatly complex cellular components being in place, then an absence of the foregoing should elicit skepticism in the mind of all but unquestioning believers.
Labels: Gene Expression