ELECTRON-MICROSCOPE INVESTIGATION OF POLYTENE CHROMOSOMES IN THE MEDITERRANEAN FRUIT-FLY CERATITIS-CAPITATA

Ultrastructural analyses of polytene chromosomes from male pupal orbit al bristle cells and from larval salivary glands of Ceratitis capitata were carried out. It was shown that chromatin complexes corresponding to the X chromosome heterochromatic network are surrounded by materia l containing ribonucleoprotein (RNP) granules 250-300 Angstrom (1 Angs trom = 0.1 nm) in diameter. RNP granules of similar size surround the spherical Y chromosome. These data point out the presence of transcrip tional activity in both of these chromosomes. The absence of clear str ucture in chromosomal regions situated between large bands in both typ es of tissues was observed. These results support the hypothesis of we ak synapsis between chromatids or small chromomeres of polytene chromo somes in this species. In addition, we describe a specific puff reveal ed in both orbital trichogen cells and salivary glands that is morphol ogically similar to the 93D puff of Drosophila melanogaster.