Transposable elements map in a conserved pattern of distribution extending from beta-heterochromatin to centromeres in Drosophila melanogaster

In situ hybridisation to mitotic chromosomes shows that sequences homologous to different Drosophila melanogaster transposable elements are widely distributed not only in beta but also in alpha-heterochromatin. Clusters of these sequences are detected in most proximal positions. They colocalise with known satellite sequences in several regions, but are also located in places where no known sequence has been mapped so far. The pattern of hybridisation is dinstinctive and specific for each element, and presents constant features in six different D. melanogaster strains studied. The entirely heterochromatic Y chromosome contains large amounts of these sequences. Additionally, some of these sequences appear to be present in substantial quantities in the smallest minichromosome of Drosophila, Dp(1;f)1187.