Decision Tile Signaling pathway. Some labeled sequences are divided into smaller lengths as indicated by subscripts. a) Activation through a neutral signal pathway, (cyan strands), at the beginning prevents the activation strand, (gold), from causing tile binding. b) The last step of the activation pathway opens the first transducer loop (magenta). c) The central downhill transducer cascade, (magenta strands), is made energetically favorable by the gain of four base pairs at each step. Another neutral pathway, (blue strands), transmits the signal to the binding site, (blue strands at the edge of the tile), to activate it by removing a protecting strand. d) After the last transducer loop has opened, the signal may be transmitted to a neighboring tile, allowing the transmission of signals to the edge of an assembly. e) The last transducer strand can instead activate the binding site through a neutral pathway. If the tile is at the edge of an assembly, this makes the edge active and ready for the next level of assembly. Otherwise, the neutral pathway will be able to reverse and release the transducer strand, giving it another chance to pass the signal to a neighboring tile.