Yrjö Viinikka

A reinvestigation of the nucleolus-organizing regions in the salivary gland nuclei of Drosophila melanogaster.

Comparisons were made of the morphology of the proximal region of the salivary gland X-chromosome of D. melanogaster following a number of different staining procedures. Azur B was found to be the most satisfactory staining method for identification of the nucleolus. The states of eu- and heterochromatization (sensu Prokofyeva-Belgovskaya) of the bands in the proximal region—particulary striking in the mirror-image duplication of the R(1)2, ring-X, chromosome—contribute to the variability in the banding-pattern, and consequently the refractoriness of this region to cytological investigation. No nucleolus was ever found to be associated with the group of bands presumed to be the Y-chromosome.

C-banded chromosomes of three Phalaris species

SUMMARYThe karyotypes and distribution of heterochromatin on the chromosomes of Phalaris aquatica (2n = 28), Ph. minor (2n = 28) and Ph. coerulescens (2n = 14) have been established with the aid of the C-banding technique.