Ordered arrangement and rearrangement of chromosomes during spermatogenesis in two species of planarians (Plathelminthes)

摘要: The pattern of distribution telomeric DNA (TTAGGG), 28S rDNA, and 5S rDNA has been studied using fluorescence in situ hybridization (FISH) primed labelling during spermatogenesis sperm formation the filiform spermatozoa two species planarians, Dendrocoelum lacteum Polycelis tenuis (Turbellaria, Plathelminthes). In both species, positions FISH signals found with each probe sequence are constant from cell to nuclei mature sperm. Chromosome regions containing genes gathered distinct bundles spiral form. early spermatids roundish nuclei, sites a given on different chromosomes remain separate. Centromeres (marked by rDNA) gather into single cluster central region slightly elongated nucleus. During spermatid maturation, this migrates distal pole Polycelis, three clusters at ends middle moderately These retain their relative as matures. All chromosome bearing only proximal cluster. Our data suggest that structures nucleus selectively recognise specific sequences, which helps these find regular places causes clustering sequences located chromosomes. This hypothesis is supported observations other animals correlation exists between ordered arrangement same spermiogenesis.