Das W-Chromosom von Ephestia kuehniella (Lepidoptera) und die Ableitung des Geschlechtschromatins

The W-chromosome, though not conspicuous in normal metaphase chromosome preparations, can be demonstrated in early oocyte and nurse cell pachytene stages using a fluorescent Feulgen stain (BAO-S02). In such preparations, it appears as a continuously fluorescing thread, whereas Z-chromosome and autosomes give a distinct pattern of chromomeres and interchromomeres. Four γ-ray induced chromosome-fusions which had been shown genetically to include the W, combine this continuously fluorescing thread with a thread having an autosomal pattern of chromomeres, differing in the four fusion-chromosomes. Concomitantly the sex-chromatin is atypically separated into several smaller bodies in highly polyploid cells of individuals possessing these W-fusions, thus showing that sex-chromatin properties depend on the W. This abnormal behaviour of the sex-chromatin is interpreted as the result of the opposing tendencies of the autosomes to form separate chromocenters and the W-chromosome to produce a single big chromocenter during polyploidisation.