This has lead to the search for a single substance that fulfills the basic criteria of life and has the capacity to evolve into the cell-based life we know today. DNA can replicate, but that's all it can do.
Proteins can change their environments, but they have no mechanism for reproduction.
The answer lies in between DNA and proteins. In fact, the ribosome itself is made up of several rRNA molecules that are essential for its function. A closer look at transcription in the eukaryotic nucleus reveals that the initial copy of the DNA contains introns which must be spliced out before the mRNA can leave the nucleus. Since many viruses use RNA instead of DNA for their genomes, we now have in RNA a substance that can replicate and store genetic information like DNA, but also has enzymatic activity like protein, fulfilling both of the requirements originally put forth. All rights reserved.