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Origin of Life: Emergence, Self-organization and Evolution
A system-centered perspective on the origin and evolution of Life on Earth
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Between exploration and fixation III: From cells to molecules

Between exploration and fixation III: From cells to molecules | Origin of Life: Emergence, Self-organization and Evolution | Scoop.it

How long does it take to an RNA pool to find a particular structure through mutation and selection? In this computational study, Manrubia and Stich relate properties of the sequence-structure map, in particular the abundance of a given secondary structure in a random pool, with the number of replicative events that an initially random population of sequences needs to find that structure through mutation and selection. Search and fixation processes are more efficient in a wider range of mutation rates for common structures, thus indicating that evolvability of RNA populations is not simply determined by abundance.

 

Source

Stich M, Manrubia SC.

Motif frequency and evolutionary search times in RNA populations.

J Theor Biol. 2011 Jul 7;280(1):117-26. Epub 2011 Mar 21.

 

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Between exploration and fixation I

Between exploration and fixation I | Origin of Life: Emergence, Self-organization and Evolution | Scoop.it

Evolution is a tricky game between exploration and fixation. Extremely high mutation rates (MRs) lead to error catastrophe. Conversely, unusually low MRs inhibit adaptation to changing environments.

Montero and co-workers investigate the time a phenotype takes to reach fitness peak as function of both fitness landscape and its mutation rate. Researchers evaluate the average time that the system takes to reach a final steady state of simple models of populations formed by self-replicative sequences (quasispecie).

 

Source:

Arturo Marína, Héctor Tejeroa, Juan Carlos Nuñob, Francisco Monteroa.

Characteristic time in quasispecies evolution

Journal of Theoretical Biology Volume 303, 21 June 2012, Pages 25–32

 

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Between exploration and fixation II: When you cannot stop

Between exploration and fixation II: When you cannot stop | Origin of Life: Emergence, Self-organization and Evolution | Scoop.it

Evolution is a tricky game between exploration and fixation, we said. True, if you do not need to win the evolutionary arms race against your opponent (predator/parasite).

Yomo and Kashiwagi report about the phenotypic and genomic changes in experimental coevolution of RNA bacteriophage Qβ and Escherichia coli. They observed how the phenotypes and genotypes of coevolving parasite-host pairs change through the arms race. Copropagation experiments with Escherichia coli and the lytic RNA bacteriophage Qβ in a spatially unstructured environment revealed continuous adaptation and counter-adaptation: “E. coli first adapted by developing partial resistance to infection and later increasing specific growth rate. The phage counter-adapted by improving release efficiency with a change in host specificity and decrease in virulence. Whole-genome analysis indicated that the phage accumulated 7.5 mutations, mainly in the A2 gene, 3.4-fold faster than in Qβ propagated alone. E. coli showed fixation of two mutations (in traQ and csdA) faster than in sole E. coli experimental evolution.”

 

Source:

Kashiwagi A, Yomo T.

Ongoing phenotypic and genomic changes in experimental coevolution of RNA bacteriophage Qβ and Escherichia coli.

PLoS Genet. 2011 Aug;7(8):e1002188. Epub 2011 Aug 4.

 

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