Evolution of Molecules

Abstract

Capability of self-replication is a unique feature of polynucleotides. Their properties represent the ultimate molecular basis of biochemical and biological evolution. The kinetics of self-replication can be approached theoretically by means of ordinary differential equations (O.D.E.). Depending on the nature of the mechanism of replication we are dealing with O.D.E.’s which have different properties. Template induced replication leads to competition between polynucleotide sequences. Stable mutant distributions called “quasispecies” are formed, when the mechanism of replication is accurate enough. The two most important features of Darwinian evolution variability through mutations and optimization of the replication rate through selection can be observed at the molecular level already. By means of higher order terms competition can be suppressed provided some conditions are fulfilled. Then, the replicating elements cooperate. A rigorous proof has been presented which relates cooperation to the formation of a closed loop of catalytic interactions. Such a closed positive feedback loop has been called a “hypercycle”. Cooperation of replicating elements allows to develop new properties of the system. These new properties are established on the expenses of global optimization. Second order catalysis hinders the system to approach the global optimum of the rate of replication.