Self-replication in a test-tube

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Discussion Overview

The discussion centers around the concept of self-replication in RNA enzymes, exploring the implications of such systems for understanding the origins of life and the definition of life itself. It includes theoretical considerations, definitions of life, and references to the RNA world hypothesis.

Discussion Character

  • Debate/contested, Conceptual clarification

Main Points Raised

  • Some participants highlight that the self-replicating RNA enzymes created by Joyce and Lincoln exhibit life-like qualities, such as indefinite self-replication and mutation.
  • Others question whether RNA enzymes can be considered living entities, suggesting that replication and evolution alone may not suffice for defining life.
  • A participant references the RNA world hypothesis, proposing that there was a time when RNA could replicate and evolve independently under certain conditions on early Earth.
  • Another participant argues that the definition of life being based solely on replication and evolution is overly broad, citing software that can also replicate and evolve.
  • Some participants assert that if an entity can replicate and evolve, it should be classified as living.

Areas of Agreement / Disagreement

Participants express differing views on whether self-replicating RNA enzymes should be classified as living entities, with no consensus reached on the definition of life itself.

Contextual Notes

The discussion reflects varying interpretations of what constitutes life, highlighting the complexity of defining life based on replication and evolution. There are unresolved questions regarding the criteria for life and the implications of the RNA world hypothesis.

Who May Find This Useful

Readers interested in the origins of life, definitions of life, RNA biology, and theoretical models of self-replication may find this discussion relevant.

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Self-Sustained Replication of an RNA Enzyme

Tracey A. Lincoln and Gerald F. Joyce

Departments of Chemistry and Molecular Biology and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.

Abstract:

An RNA enzyme that catalyzes the RNA-templated joining of RNA was converted to a format whereby two enzymes catalyze each other’s synthesis from a total of four oligonucleotide substrates. These cross-replicating RNA enzymes undergo self-sustained exponential amplification in the absence of proteins or other biological materials. Amplification occurs with a doubling time of about one hour, and can be continued indefinitely. Populations of various cross-replicating enzymes were constructed and allowed to compete for a common pool of substrates, during which recombinant replicators arose and grew to dominate the population. These replicating RNA enzymes can serve as an experimental model of a genetic system. Many such model systems could be constructed, allowing different selective outcomes to be related to the underlying properties of the genetic system.

Citation: T. A. Lincoln and G. F. Joyce, Science, 2009, DOI: 10.1126/science.1167856


Chemists edge closer to recreating early life

09 January 2009

A test tube based system of chemicals that exhibit life-like qualities such as indefinite self-replication, mutation, and survival of the fittest, has been created by US scientists. The researchers say their perpetually replicating RNA enzymes take us a step closer to understanding the origins of life on Earth, as well as to how life may one day be synthesised in the lab.

The system, created by Gerald Joyce and Tracey Lincoln at the Scripps research institute in La Jolla, California, involves a cross-replicating pair of ribozymes (RNA enzymes), each about 70 nucleotides long, which catalyse each other's synthesis. So the 'left' ribozyme templates the synthesis of the 'right', which in turn templates the 'left' and so on, building each other via Watson-Crick base pairing.

http://www.rsc.org/chemistryworld/News/2009/January/09010901.asp

Isn't that exciting?
 
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RNAs aren't living entities right?
 
if it can replicate and evolve then its living

and according to the rna world hypothesis there was a time when conditions on Earth were such that rna by itself could do just that
 
Last edited:
granpa said:
if it can replicate and evolve then its living

That's a very poor (or overy broad, if you prefer) definition of life. We have software which can do both of those things. Are they life?
 
yes.
 
granpa said:
if it can replicate and evolve then its living

Huh?
 

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