SELECTIVE STAINING OF X-CHROMOSOME SEGMENTS IN SCHISTOCERCA-GREGARIA AFTER DENATURATION AND REASSOCIATION PROCEDURES

The DNA of fixed mitotic and meiotic chromosomes and of spermatides of Schistocerca gregaria males was heat denaturated and then differentially reassociated in a Giemsa buffer or in acridine orange buffer solution. After this procedure, two to three large, selectively stained regions are seen in the X chromosome of spermatocytes and spermatides. Denaturation and reassociation experiments have shown that after differential reassociation such a selective stainability of chromosome regions is characteristic for the presence of fast-reassociating, i.e., repetitive DNA (Stockert and Lisanti, 1972). The possible presence of repetitive DNA in the X chromosome regions concerned can not be the only reason for the occurrence of the heavily stained segments after reassociation because (1) these segments are obtained in positively heteropycnotic X chromosomes, but not in negatively heteropycnotic Xs and (2) they do not occur in positively heteropycnotic X chromosomes when the histones have been extracted before the denaturation and reassociation processes. Contrary to the latter statement, the heavily stained X chromosomal regions are preserved when the histones are removed after the denaturation and reassociation steps. - It is assumed that the heavily stained X chromosome segments represent DNA reassociation complexes which are only formed if histones are present. It is discussed whether the formation of the X chromosome complexes depends on a specific chromatin configuration within positively heteropycnotic X chromosomes. © 1979 Springer-Verlag.