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Evolution in vitro: analysis of a lineage of ribozymesBackground: Catalytic RNAs, or ribozymes, possessing both a genotype and a phenotype, are ideal molecules for evolution experiments in vitro. A large, heterogeneous pool of RNAs can be subjected to multiple rounds of selection, amplification and mutation, leading to the development of variants that have some desired phenotype. Such experiments allow the investigator to correlate specific genetic changes with quantifiable alterations of the catalytic properties of the RNA. In addition, patterns of evolutionary change can be discerned through a detailed examination of the genotypic composition of the evolving RNA population. Results: Beginning with a pool of 10(13) variants of the Tetrahymena ribozyme, we carried out in vitro evolution experiments that led to the generation of ribozymes with the ability to cleave an RNA substrate in the presence of Ca2+ ions, an activity that does not exist for the wild-type molecule. Over the course of 12 generations, a seven-error variant emerged that has substantial Ca(2+)-dependent RNA-cleavage activity. Advantageous mutations increased in frequency in the population according to three distinct dynamics--logarithmic, linear and transient. Through a comparative analysis of 31 individual variants, we infer how certain mutations influence the catalytic properties of the ribozyme. Conclusions: In vitro evolution experiments make it possible to elucidate important aspects of both evolutionary biology and structural biochemistry on a reasonable short time scale.
Document ID
20040089672
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Lehman, N.
(The Scripps Research Institute La Jolla, California 92037, United States)
Joyce, G. F.
Date Acquired
August 21, 2013
Publication Date
January 1, 1993
Publication Information
Publication: Current biology : CB
Volume: 3
Issue: 11
ISSN: 0960-9822
Subject Category
Exobiology
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Exobiology

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