Figure 2.

List of the major rRFs reported in the literature. The rRFs have been classified beyond the provenance from the 18S, 5.8S, 28S, ITS1, or ITS2 rRNA. For each rRF, the name, species of origin, and length are specified. An rRF described in a species may not be conserved in other species. Each organism has different levels of regulation and organization, and, although similarities exist between organisms, the occurrence and sequence of rRFs in a given rRNA region may be different. For example, ITS1 contains MER45C, which may be specific to vertebrates. Yet, in Drosophila a microRNA is shown in that region.