Abstract: Electrophoretic separation in a slab gel and blotting of the resulting zone pattern onto a membrane are both performed in a single tank cell which contains separation electrodes along opposing vertical walls and blotting electrodes horizontally arranged above and below the level designated for the gel placement. The blotting electrode situated below the gel is an array of parallel wires arranged to simulate a plate electrode. The cell is operated in separatory and blotting modes, in which the separation and blotting electrodes, respectively, are separately energized. During the separatory mode, the wires in the array forming the lower blotting electrode are electrically isolated from each other to permit each to adjust to the voltage of the buffer immediately surrounding it.