The relationship path through operon edge and similarity edge. Given a reference pathway, its known genes are used as seeds to calculate the shortest distances to candidate genes. For example, gene1 and gene2 are connected with the same candidate gene. The path from gene1 to candidate gene (path1) is noted as solid line, and gene2 to candidate gene (path2) as dashed line. The paths are both constructed by operon edge (colour arrow) and similarity edge (solid or dashed line).