A study of heterochromatin in Drosophila nasuta by the 5-bromodeoxyuridine-Giemsa staining technique.

Larval brain ganglia of Drosophila nasuta were cultured in vitro in the presence of 5-bromodeoxyuridine for 1 or 5 h at 24 degrees C and the air-dried chromosome preparations stained by the Hoechst 33258-Giemsa technique to reveal bromodeoxyuridine induced sister chromatid differentiation. In 1 h as well as 5 h preparations, 10-15% of well spread metaphase plates show a sister chromatid differentiation in only C-band heterochromatin regions of different chromosomes. We infer that this sister chromatid differentiation in all heterochromatic regions is seen after bromodeoxyuridine incorporation for only one replication cycle and is related to the presence of asymmetric A-T rich satellite sequences in all the C-band regions of D. nasuta karyotype.