Simultaneous detection of SCE and Q-bands on human chromosomes by a double-staining technique

Human lymphocytes were cultured for two cell cycles in the presence of bromodeoxyuridine (BrdU), and the resulting metaphase chromosomes were first stained with quinacrine mustard (QM) and then, immediately afterwards, with Hoechst 33258, without any intermediate destaining. Both Q-banding patterns and sister chromatid differential staining were photographed subsequently on the same metaphase using two different filter blocks of the fluorescence microscope.