title: Copy number and distribution of P and I mobile elements in Drosophila melanogaster populations.
abstract: The distribution of the number of copies of P and I transposable elements per genome was investigated by in situ hybridization for a large set of Drosophila melanogaster strains. These included the P, Q and M' types of the P-M system of hybrid dysgenesis. P element copy number varied widely (range 5-59). P and Q strains had around 40 copies whereas M' strains generally had lower numbers (between 5 and 35) with one extreme value (52). The copy number of I elements appeared to be precisely regulated, as no strains were found outside the 15 +/- 5 range. The number of copies of the two families were independent. An excess of P copies on the X chromosome compared with the autosomes was found for the P and Q strains, but not for M' strains. Among X-inserted P sites, a very high frequency of occupation was found at the tip of the X chromosome (cytological site 1A), especially for P and Q strains. The possible regulatory role in the P-M system of X-inserted P sites is discussed.
authors.affiliation: Laboratoire de Génétique des Populations Université Paris, France.
authors.forename: S
authors.initials: S
authors.lastname: Ronsseray
authors.forename: M
authors.initials: M
authors.lastname: Lehmann
authors.forename: D
authors.initials: D
authors.lastname: Anxolabéhère
mesh_terms: D000818:Animals; D004251:DNA Transposable Elements; D004331:Drosophila melanogaster / Q000235:genetics* / Q000502:physiology; D005784:Gene Amplification; D009024:Morphogenesis; D009693:Nucleic Acid Hybridization; D014960:X Chromosome / Q000648:ultrastructure*
chemical_list: D004251:DNA Transposable Elements