Schematic representation of suspicious links. In the figure, arrows represent activations and right angles inhibitions. Dotted lines correspond to the links that are topologically suspicious, i.e., those for which a secondary regulatory pathway mediated by a third gene is registered and whose sign is coherent. For example, the link connecting nodes 1 and 2 is considered suspicious because of the existence of the pathway 1 to 3 and 3 to 2. The same happens for the link between nodes 3 and 4. In both cases, the condition that the product of the two links making the secondary pathway should coincide with that of the link being considered as suspicious is verified. In this sense, we have also included a case in which the latter condition does not hold: the edge linking node 1 to node 5 is not suspicious because although a two-nodes cascade connecting the same nodes exists, (i.e. 1 to 3 and 3 to 5) it is not sign coherent.