Document Detail


Evolution without speciation but with selection: LUCA, the Last Universal Common Ancestor in Gilbert's RNA world.
MedLine Citation:
PMID:  15011140     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
This is not an attempt to analyze the Last Universal Common Ancestor (LUCA) to understand the origin of living systems. We do not know what came before Gilberts' RNA world. Our analysis starts with the RNA world and with genes (biological replicators alla Dawkings) made up of RNA proteins with enzymatic catalytic functions within units that are not yet modern cells. We offer a scenario where cellular entities are very simple and without individuality; they are only simple primary units of selection (the first level of selection) in which replicators compete in the most Darwinian manner, totally deprived of cooperation and interactions among genes. The information processing system of this RNA world is inaccurate and inefficient when compared to that found in organisms that came later. Among the "genes" and the entities that harbor them, high mutation rate was the most prevalent source of variability and the only inheritance was through lateral gene transfer of mobile elements. There were no chromosomes or any other genomic organization. As millions of years accumulated, complex and organized biological structures and processes evolved thanks to the variability mustered up mostly by lateral gene transfers and mutations. With micro- and mini-satellites, lateral gene transfers became indispensable devices of selection to mold variability. Competition and Darwinian selection gave way to a new transition in evolution, one I consider ineluctable, in which cooperation among interactive genes prevailed for the sake of higher fitness. Compartmentalization constituted a major transition in evolution that spurted new types of genome organization. Minichromosomes is one of these; cellular membranes and cytoplasmic structures completed the picture of the primitive cell. However, the much talked about phylogenetic tree does not exit in that ancient LUCA. The tree has no organism at its base; only clusters of genes evoke a fragile beginning for the increasingly complex cell types that were to emerge later.
Authors:
Hugo Hoenigsberg
Publication Detail:
Type:  Journal Article     Date:  2003-12-30
Journal Detail:
Title:  Genetics and molecular research : GMR     Volume:  2     ISSN:  1676-5680     ISO Abbreviation:  Genet. Mol. Res.     Publication Date:  2003  
Date Detail:
Created Date:  2004-03-10     Completed Date:  2004-06-07     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  101169387     Medline TA:  Genet Mol Res     Country:  Brazil    
Other Details:
Languages:  eng     Pagination:  366-75     Citation Subset:  IM    
Affiliation:
Institute of Evolutionary Genetics and Molecular Biology, Universidad Manuela Beltran, Bogotá D.C., Colombia. hoenisbe@umb.edu.co
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MeSH Terms
Descriptor/Qualifier:
Animals
Evolution, Molecular*
Models, Theoretical*
Phenotype
RNA*
Selection, Genetic*
Chemical
Reg. No./Substance:
63231-63-0/RNA

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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