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The roads to and from the RNA world
Jason P Dworkin1, Antonio Lazcano, Stanley L Miller
1Laboratory for Extraterrestrial Physics, Code 691, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA. jason.dworkin@nasa.gov
Journal of Theoretical Biology
|April 18, 2003
Summary
Early life likely used RNA for both genetic and catalytic functions. This study explores whether DNA or proteins followed RNA, considering metabolic and molecular stability arguments.
Area of Science:
- Origin of Life studies
- Molecular Evolution
- Biochemistry
Background:
- The RNA world hypothesis posits early life used RNA for genetic and catalytic functions.
- The sequence of molecular evolution after the RNA world remains debated, specifically the emergence of DNA and proteins.
- The pre-RNA world, preceding RNA's dominance, is also an area of limited discussion.
Purpose of the Study:
- To explore the evolutionary pathways following the RNA world.
- To discuss whether DNA or proteins emerged first after RNA.
- To consider the pre-RNA world and its potential precursors.
Main Methods:
- Review and synthesis of existing metabolic and molecular stability arguments.
- Comparative analysis of ribose and 2-deoxyribose properties.
- Evaluation of evolutionary parsimony for different scenarios.
Main Results:
- Metabolic arguments suggest RNA genomes may have preceded DNA.
- Arguments based on enhanced stability, reactivity, and solubility of 2-deoxyribose support DNA preceding RNA.
- The scenario of DNA following RNA is considered more parsimonious.
Conclusions:
- Both DNA-before-RNA and RNA-before-DNA scenarios are plausible based on different lines of evidence.
- The precise order of emergence of DNA and proteins after the RNA world requires further investigation.
- Understanding these transitions is crucial for reconstructing the earliest history of life.