Ribozyme function is likely to require strands of RNAs that are composed of at least 30-40 nucleotides.
Research from James Ferris' group at Rensselaer Polytechnic Institute suggests that the formation of long strands of RNA may have been catalyzed by clays such as montmorillonite.
The charged clay surface attracts the nucleotides and the increased local concentration of nucleotides causes bond formation between nucleotides, forming a polymer of RNA (illustrated in the animation on left).
Another possibility is that strands of RNA could have formed in salty ice water. David Deamer's lab at the University of California at Santa Cruz has found that the process of freezing a dilute solution of chemically activated RNA nucleotides causes the nucleotides to become concentrated as ice crystals form, eventually resulting in the formation of strands of RNA.
Even in the absence of enzymatic catalysts, single-stranded RNAs may have been able to copy strands of RNA through template-directed polymerization. This process is shown in the animation on the left, and is based on experiments performed in Jack Szostak's Lab (MGH/Harvard) using chemically activated nucleotides.
This process of non-enzymatic replication, however, is likely to have been slow and error-prone. Eventually, this mechanism of RNA replication is likely to have been replaced by a more reliable catalyst, such as a ribozyme. Scientists hypothesize that a ribozyme that was capable of making copies of other RNAs, called a replicase, evolved very early in life's history.
The animation on the lower left shows a theoretical replicase copying a template strand of RNA. While the structure of the replicase shown in the animation is based on an existing ribozyme that is capable of carrying out the basic steps of a replication reaction, a true replicase that is capable of copying an RNA copy of itself has not yet been isolated in a laboratory.