Introduction

Long before science began, the question of the origin of life was answered by religion and mythology. With the work of Lamarck and Darwin, science started to try to give new answers to an old question. The theory of Darwinian evolution describes the origin of biological information. In general, an evolving system (i.e., an information-gaining system) is able to metabolize, to self-replicate, and to undergo mutations (as was stated by Oparin in 1924). Thus self-replication is one of the three criteria that enable us to distinguish nonliving from living systems. Since nucleic acids carry the inherent ability for complementary base-pairing (and replication), they are very likely candidates to have been the first reproducing molecules. Kuhn and others (Crick 1968; Orgel 1968; Eigen and Schuster 1979; Kuhn and Waser 1981; for a review, see Joyce 1989) have drawn the picture of an RNA world that might have existed before translation was invented. This picture was supported by the finding that RNA (and also DNA) can act as an enzymelike catalyst (Sharp 1985; Cech 1987; Joyce 1989; Breaker and Joyce 1994). It is a challenge for organic and bioorganic chemists to trace back the original path of evolution by “reinventing” simple self-replicating systems in the lab and to learn more about the principles of replication on a molecular scale.

A simple three-step model can be used to conceptualize the process of molecular self-replication (Figure 14.1). In this model, the template molecule T is self-complementary and thus able to autocatalytically augment itself. In the first step, the template T reversibly binds its constituents A and B to yield a termolecular complex M.