Catastrophe

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All self-replicating systems are susceptible to random eradication events. There are several catastrophes that have been identified by Eigen et al. and Niesert et al., using mathematical models and computer simulations of RNA populations respectively.

Contents

Eigen's error catastrophe

Eigen et al. proposed that over time, an RNA population accumulates errors through replication, which eventually reach a point where they interrupt the sequences required for replication. When this happens, the population loses the ability to replicate and succumbs to an error catastrophe[1].

Niesert's catastrophes

Niesert et al. built on Eigen's error catastrophe using a number of computer simulations and identified three more catastrophes.

The selfish RNA catastrophe begins with the mutation of a single RNA molecule that makes it much faster at replicating. However, the mutation removes its ability to contribute any useful catalytic activity to the population, so it rapidly replicates and exploits all available resources. Eventually, the entire population 'dies out'.

The short-circuit catastrophe occurs as a result of a mutation in a single RNA molecule that is part of a metabolic cycle. The mutation prevents the RNA molecule from catalysing its own step in the reaction pathway and eventually, the cycle breaks down.

The population collapse catastrophe is caused by a random event that removes all of an intermediate product in a metabolic cycle. With the intermediate missing, later steps in the reaction pathway stop and the entire system stops working[2].

Catastrophes and population size

Niesert et al. also found that the probability of the selfish RNA and short-circuit catastrophes occurring is directly proportional to the size of the RNA population, as both are caused by a mutation in a single RNA molecule. On the other hand, the probability of the population collapse catastrophe is inversely proportional to population size, as a larger population is more capable of surviving the loss of an intermediate in a reaction pathway. Due to this, there is thought to be a very narrow band of population sizes that have a low enough probability of each catastrophe occurring that the population is likely to survive and evolve[3].

References

  1. Eigen M, Schuster P. The Hypercycle: The Principle of Natural Self-Organization. Die Naturwissenschaften [Internet]. 1977;64(11):541-565. Available from: https://pdfs.semanticscholar.org/eefb/7127bbf856e30ef16980d01297b830d3c2d5.pdf
  2. Niesert U, Harnasch D, Bresch C. Origin of Life Between Scylla and Charybdis. Journal of Molecular Evolution [Internet]. 1981;17:348-353. Available from: https://link.springer.com/content/pdf/10.1007%2FBF01734356.pdf
  3. Niesert U, Harnasch D, Bresch C. Origin of Life Between Scylla and Charybdis. Journal of Molecular Evolution [Internet]. 1981;17:348-353. Available from: https://link.springer.com/content/pdf/10.1007%2FBF01734356.pdf
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