Quasispecies: from molecular Darwinism to viral diseases Authors Esteban Domingo Abstract The microbial world offers the most direct evidence of natural selection, the central concept of Darwins theory. The evidence of the extraordinary biological diversity on the molecular level, and its parallelism to morphological diversity observed by Darwin, has continued to increase until our days. It affects all types of organisms and the parasites they contain, including viruses. Some experimental designs with RNA viruses have allowed us to dissect the basic processes of biological evolution: genetic variation, competition and selection. The population dynamics that characterizes RNA viruses is known as quasispecies dynamics, which refers to a theory of the origin of life developed four decades ago, which proposes that the first elements equipped with autonomous replication were constructed, approximately 4000 million years ago, from small molecules, equal or similar to the RNA we know today. These primitive molecules were able to evolve thanks to the continuous production of erroneous copies, as we observe in the current RNA viruses. Today, quasispecies dynamics allows viruses to survive in the organisms they parasite and respond to selective pressures that attempt to stop their multiplication (components of the immune system, drugs, etc.) Among RNA viruses there are well-known human pathogens such as the virus that causes AIDS, the viruses associated to the different forms of hepatitis, and different emerging and reemerging viruses, so the implications of the dynamics of quasispecies for the control of viral diseases are very clear. Research has established that within viral populations there are interactions between components of the same quasispecies, which behave/operate as a selection unit. This observation represents a fundamental change with regard to what was thought a few years ago, in the sense that the behavior of viruses is not necessarily predictable by the behavior of the individual genomes that make up a population. This has several theoretical, as well as medical, implications. Downloads Text complet (Català) Published 2010-06-21 Issue 5-2 Section Celebration of the Darwin Year 2009 License This work is subject, unless the contrary is indicated in the text, the photographs or in other illustrations, to an Attribution —Non-Commercial— No Derivative Works 3.0 Creative Commons License, the full text of which can be consulted at http://creativecommons.org/licenses/by-nc-nd/3.0/. You are free to share, copy, distribute and transmit the work provided that the author is credited and reuse of the material is restricted to non-commercial purposes only and that no derivative works are created from the original material.