An apparatus for casting an agarose gel and for conducting an electrophoresis process is disclosed. An electrophoresis tank (106) supports a gel casting deck (202) having open ends (210) which are sealed by wedge dams (302) to form a cavity for containing the molten agarose as it gels. The wedge dams (302) are pulled downward by gravity into wedge-shaped slots. The weight of the wedge dams (302) in the wedge slots presses the wedge dams (302) against the open ends (210) of the gel casting deck (202) so as to provide a substantially fluid-tight seal. The gel casting deck (202) has sidewalls whcih are slanted toward one another in the upwards direction so that when the gel is submerged in buffer solution during electrophoresis, the gel's tendency to float is substantially impeded. The combs (408) which form wells in the gel are referenced to the sides (208) of the gel casting deck (202) itself so as to ensure uniformity and accuracy of well depth. Safety features prevent the electrophoresis tank from functioning if removed from its protective housing.