Prof. Dieter Söll: "The Genetic Code Revisited – Four Decades after Francis Crick"
von 16:00 bis 17:00
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Professor Dieter Söll
Department of Molecular Biophysics and Biochemistry, Yale University
"The Genetic Code Revisited – Four Decades after Francis Crick"
At the time of its elucidation the genetic code was suggested to be universal in all organisms, and the result of a ‘frozen accident’ unable to evolve further even if the current state were suboptimal. How do we see the genetic code today – forty years after the familiar ‘alphabet’ was established? Of course, the ‘genetic code’ is the product of its interpretation by the translational machinery (e.g., tRNA and aminoacyl-tRNA synthetases) and it is only static as long as the components of this machinery do not evolve or are strictly conserved between organisms. Based on our current knowledge why do we consider the genetic code to be expanding? The ancient essential process of ribosomal protein synthesis requires twenty sets of aminoacyl-tRNAs, one for each canonical amino acid, for the correct transmission of the genetic information. Since Crick proposed his adaptor hypothesis it was commonly accepted that all organisms or organelles possess twenty aminoacyl-tRNA synthetases, each enzyme specific for attaching one amino acid to tRNA. It is now clear that aminoacyl-tRNA formation is far more varied, as the biosynthetic routes vary greatly in nature. The routes to these tRNAs differ not only in the three domains of life but also vary among organelles.