Figure 3From: Predicting RNA secondary structure by the comparative approach: how to select the homologous sequencesBase pair substitutions in stems. Double mutations are supported or disadvantaged depending on the stability of the intermediate state. As the GU pair is the most stable and the least deleterious of the intermediate states, the double substitutions which use the GU intermediate state (AU ? GC and UA ? CG) may occur more frequently than the others.Back to article page