ON PRODUCING MORE COMPLEXITY THAN ENTROPY IN REPLICATION

RNA replication in the bacteriophage Q beta system can, in principle, transmit sequence complexity at a higher rate than it Increases entrop y. Expanding the variety of nucleotides, through novel base pair inter actions, would move the threshold at which synthesis produces more com plexity than entropy away from near equilibrium while accelerating the system approach to equilibrium. A decrease in sequence complexity dur ing polymerization, leading to a many-to-one monomer correspondence wi th template, cannot be reversed, owing to symmetry restrictions. In te rms of the kinetic mechanism, uncertainty associated with the the path of depolymerization yields a path entropy which selectively prolongs the reverse reaction. Together with an elevation in thermodynamic entr opy, therefore, there are two possible sources of irreversibility in a physical process. Some implications of kinetic irreversibility are co nsidered in relation to the second law of thermodynamics and to the pr ocessing and translation of mRNA.