RNA World Hypothesis

The RNA world hypothesis proposes that a world filled with RNA-based life predates current DNA-based lifeforms

RNA has two key qualities that would have allowed it to function in this manner:

RNA can self-replicate

  • RNA is able to store information in a sequence composed of four recurring nucleotides (similar to DNA)
  • Short sequences of RNA are able to be accurately duplicated to form identical RNA molecules

RNA can act as a catalyst

  • Modern cells use RNA catalysts (called ribozymes) to remove introns from mRNA and help synthesise new RNA molecules
  • In ribosomes, rRNA functions as the catalytic component and plays a pivotal role in peptide bond formation

RNA is the only molecule that is capable of both self-replication and catalytic functioning, but has since been superseded:

  • DNA, through its superior chemical stability (double helical structure) has taken over as the data storage form
  • Protein, through its greater variability (20 amino acids as opposed to 4 nucleotide bases) has taken over as the catalytic form
  • RNA remains as a transitional form between DNA and protein, suggestive of its multi-faceted origins 

Summary of the RNA World Hypothesis

RNA world hypothesis