RNA Replication
Biebricher, C.K.
Max-Planck-Institute for Biophysical Chemistry, Am Fassberg 11,
D-37070 Göttingen, Germany
Replication is a crucial step in the origin of life. It is now generally accepted that the primary genetic material was RNA rather than DNA. In a series of experiments, Orgel and coworkers have shown that partially primed single-stranded RNA can be completed to double strand RNA under reasonably prebiotic conditions. This reaction is not providing autocatalytic replication, however, because the double strand can not be reactivated to serve as a template for further replication rounds. Reactivation of the double strand by thermic melting has been proposed, but is unlikely to occur under plausible conditions. On the other hand, autocatalytic RNA replication can be catalysed by a single enzyme, the RNA replicase, which is coded for by many RNA viruses. This replication has two remarkable features: (1) the replicase is highly selective in accepting templates for replication, suggesting a participation of the RNA in the replication process, and (2) it synthesizes a complementary replica strand and recycles the template strand, both as single strands. Sequence comparison of replicable RNA species suggests that the secondary structure of the RNA participates in the post-replicative melting. Replicating RNA has been show to undergo efficient Darwinian evolution, the ability of an RNA to direct its own synthesis being a particularly simple phenotypic expression of a genotype. While DNA-dependent RNA polymerases also catalyse RNA replication when instructed by a specific RNA, no non-enzymic or ribozymic replication system has yet been found. I suggest that single-stranded RNA replication has been the first prebiotic system capable to Darwinian evolution.
| LOCATION |
DATE |
TIME |
| Lecture Hall II |
Sunday, April 5 |
04:30 pm |