Specific heterochromatic banding of metaphase chromosomes using nuclear yellow

The bis-benzimidazole compound nuclear yellow (NY) belongs to the same chem ical family as the DNA binding fluorochromes Hoechst 33258 and Hoechst 3334 2, Spectroscopic studies of NW alone and in the presence of calf thymus DNA show high DNA binding affinity and behavior similar to the Hoechst fluoroc hromes above, Mitotic metaphase chromosomes from Balb/c mice stained with N Y show C-banding and weak G/Q-banding, both of them disappearing after dist amycin A (DA) or methyl green (MG) counterstaining, The same staining of hu man metaphase chromosomes from lymphocyte cultures, however, reveal only fa int G/Q-banding (NY) and a characteristic DA- DAPI-like banding (NY-DA, NY- MG). Image analysis of NY stained human chromosomes, confirms that NY is su itable for studying polymorphisms affecting size in the pericentromeric het erochromatin of pairs 1, 9 and 16, and shows significant enhancement of NY fluorescence induced by DA in DA-DAPI heterochromatin. Our spectroscopic an d cytological results show that NY, either alone or counterstained with DA or MG, can be used for DNA cytochemistry and chromosome banding, Possible m echanisms for the banding patterns induced by NY are discussed.