Staining of constitutive heterochromatin in mammalian chromosomes with a new fluorochrome.

Abstract A simple and direct fluorescence staining procedure is described in this note by which chromosomal segments of constitutive heterochromatin and (in the mouse) sites of repetitious DNA can be visualized in mammalian chromosomes with a benzimidazol derivative “33258 Hoechst” belonging to a class of DNA-binding fluorochromes different from compounds of the Q-series [3, 4]. In the mouse ( M. musculus ) and the tobacco mouse ( M. poschiavinus ) the centromeric regions display bright fluorescence. However, in the (North African) hedgehog ( Aeth. algirus ), distally located autosomal segments of heterochromatin fluoresce weakly or are negative. This finding is similar to the behaviour of the respective heterochromatin types as shown by the staining method of Arrighi & Hsu [2].