 Attempts have been made to model the tertiary structure of other group II introns, such as the ai5γ group IIB intron, using a combination of programs for homology mapping onto known structures and "de novo" modeling of previously unresolved regions.Group IIC are characterized by a catalytic triad made up by CGC, while Group IIA and Group IIB are made up by AGC catalytic triad, which is more similar to the catalytic triad of the spliceosome.It is believed that the Group IIC are also smaller, more reactive and more ancient.