Saturation of autoradiography. The figure shows a minority variant mixed sample exposed to autoradiography film for differing intervals. Lane A shows a 5 minute exposure where the mutant band is not visible. Lane B is a 10 minute exposure where the mutant band (see arrow) becomes visible. Lanes C and D show 15 and 20 minute exposures, respectively. In these lanes the background intensity begins to obscure the minority variant mutant band.