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9 Introns and the RNA World

Walter Gilbert, Sandro J. De Souza


The RNA World is a hypothesis about the origin of life based on the view that the most critical event is the emergence of a self-replicating molecule, a molecule that can both copy itself and mutate and, hence, evolve to more efficient copying (Gilbert 1986). Evolution works on variation and selection, and selection is always measured in terms of more efficient multiplication, the ability to make more of the entity in question. The concept of an RNA World is a way of answering the basic problem of what was the molecular biology involved at the beginning of life. Our understanding of the molecular basis of biology today is in terms of a genetic material, commonly DNA, translated through an apparatus involving RNA and the mechanism of protein synthesis to specify the positions of 20 amino acids in protein enzymes. That picture of life, in which the genetic material is of one chemical kind, DNA, made up of four bases, a second chemical, RNA, is used for structural and transfer purposes, and the enzymatic activities in the cell are a third chemical kind made up of 20 ingredient amino acids, creates a complex paradox in trying to formulate how life could have begun. This paradox was resolved by two realizations. One was that RNA is likely to be more primary than DNA, but the picture of an RNA–protein world, in which RNA is the genetic material specifying the positions of amino acids in proteins, still left one with a complex...

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