Professor Neil Straus explains how the model that came first is a molecule that can be both a gene and an enzyme. The answer to the evolutionary dilemma is RNA.
This “RNA World” theory has actually been given new impetus by recent revelations in gene regulation and molecular structural analysis. A host of RNA molecules have now been discovered that are ribozymes – RNA with enzymatic activity. One of these ribozymes can catalyze the accurate polymerization of RNA on an RNA template. Detailed structural analysis of the ribosome has now revealed that the ribosome is a ribozyme and that it is the RNA portion of the ribosome that catalyses the synthesis of proteins. This means that RNA can be the repository of genetic information, that can be synthesized into ribozymes. These ribozymes in turn and replicate the information that dictates their own synthesis in addition to the synthesis of ribosomes and other ribosymes that can eventually synthesize protein. There is no need for the chicken and egg dilemma. RNA was enough to kick-start the complex process of evolution some 4 billion years ago.
You can read Straus’ complete article and see models of RNA in its various forms at Indigo Molecular Models