FIGURE 2.

Topology of the largest neutral net in the (a) HP′, (b) HPmax, (c) AB′, and (d) ABmax models. Sequences encoding for the same structures (provided in Fig. 1) are represented by solid symbols (dots, circles, triangles, etc.); and mutational connectivity by a single-point substitution between two sequences is depicted by a line joining a pair of symbols. For a given neutral net, the prototype sequence and the sequence with maximum native stability (as defined in Fig. 3 below) are marked, respectively, by an open circle and an open square. A neutral net conforms to the superfunnel paradigm if both conditions are satisfied by the same sequence. In a, c, and d, different symbols denote sequences with different Hamming distances from the prototype sequence (Bornberg-Bauer and Chan, 1999).