Figure 1. The structure of RNA. (a) Schematic representation of the four major bases of the ribonucleotides: adenosine (AMP) and guanine (GMP) that are both purines, and uracil (UMP) and cytosine (CMP) that belong to the pyrimidines; (b) The structure of RNA.

Figure 2. The RNA World hypothesis. The genesis of a hypothetical RNA World includes a series of events, summarized schematically in this figure, that include the abiotic synthesis of RNA monomers from common inorganic/organic molecules and their assembly into oligomers (in the likely presence of metal catalysts) that would have had to serve as templates for their own spontaneous copying or replication. At this stage, a set of catalytic RNAs may have evolved (among them, RNA‐based RNA copying molecules), and this would have sustained their exponential growth in the prebiotic environment.

Figure 3. Expression of RNA. A schematic view of the most common noncoding and coding RNA families currently described in the eukaryotic cell.

Figure 4. Products of alternative splicing. A schematic representation of alternative splicing models. Constitutive exons are shown as gray boxes, introns as horizontal lines, and alternative exons as blue–red‐shaded boxes.