title: Localisation of non-replicating heterochromatin in polytene cells of Drosophila nasuta by fluorescence microscopy.
abstract: A simple fluorescence technique is decribed to localise in situ the non-replicating alpha heterochromatin in the chromocentre region of Drosophila nasuta polytene nuclei. After incorporating 5-bromodeoxyuridine in larval salivary gland cells for one or two cycles of replication, the polytene nuclei are examined for Hoechst 33258 flourescence at pH 7.0. The non-replicating alpha heterochromatin remains brightly fluorescing as it does not incorporate any 5-bromodeoxyuridine while the rest of the replicating chromatin shows dull fluorescence due to the quenching of Hoechst 33258 fluorescence by the bromodeoxyuridine substituted DNA.
mesh_terms: D000818:Animals; D006690:Bisbenzimidazole; D001973:Bromodeoxyuridine; D002467:Cell Nucleus / Q000648:ultrastructure; D004330:Drosophila; D006570:Heterochromatin / Q000032:analysis*; D066298:In Vitro Techniques; D008856:Microscopy, Fluorescence
chemical_list: D006570:Heterochromatin; D001973:Bromodeoxyuridine; D006690:Bisbenzimidazole