FIGURE 6.1 - Preparing a CHEF gel using the BioRad casting stand. (a) The parts of the casting stand. The stand is assembled by placing the large notches on the ventral surface of the end-bars over the thumb screws at the ends of the side-bars of the casting tray. The base plate is set in the casting tray and the upper and lower edges of the base plate are fitted into the lateral grooves of the end-bars. The thumb screws of the side-bars are tightened to form a water-proof seal. The comb holder and attached comb are placed in the distal comb notches on the side bars. (b) Approximately 200-250 ml of 1.0% agarose is poured into an assembled casting stand. (c) After the gel has solidified, the comb and the side-bars are removed. The gel and its underlying base plate are slid out of the casting tray and placed into the CHEF apparatus (see FIGURE 6.3).