title: A 5.9-kb tandem repeat at the euchromatin-heterochromatin boundary of the X chromosome of Drosophila melanogaster.
abstract: We present an analysis of a chromosomal walk in the region of the euchromatin-heterochromatin transition at the base of the X chromosome of Drosophila melanogaster. This region is difficult to analyse because of the presence of repeated sequences, and we have used cosmids to walk from the last euchromatic gene, suppressor of forked, towards the pericentric heterochromatin. The proximal 30-kb sequence we have isolated consists of repetitive DNA, including four tandem copies of a 5.9-kb sequence. This tandem repeat is itself a mosaic of other, mostly repeated, sequences, including part of a retrotransposon without long terminal repeats, a simple-sequence region of TAA repeats and part of a retrotransposon with long terminal repeats that has not been previously described. Although sequences homologous to these components are found elsewhere in the genome, this arrangement of repeated sequences is only found at the base of the X chromosome. It is conserved in D. melanogaster strains of different geographic origin, but is not conserved in even closely related species.
authors.affiliation: Department of Biochemistry, Imperial College of Science, Technology and Medicine, London SW7 2AZ, UK. k.ohare@ic.ac.uk
authors.forename: K
authors.initials: K
authors.lastname: O'Hare
authors.forename: B P
authors.initials: BP
authors.lastname: Chadwick
authors.forename: A
authors.initials: A
authors.lastname: Constantinou
authors.forename: A J
authors.initials: AJ
authors.lastname: Davis
authors.forename: A
authors.initials: A
authors.lastname: Mitchelson
authors.forename: M
authors.initials: M
authors.lastname: Tudor
mesh_terms: D000818:Animals; D001483:Base Sequence; D016386:Chromosome Walking; D004251:DNA Transposable Elements; D004331:Drosophila melanogaster / Q000235:genetics*; D022041:Euchromatin; D006570:Heterochromatin; D008969:Molecular Sequence Data; D020161:Physical Chromosome Mapping; D017422:Sequence Analysis, DNA; D020080:Tandem Repeat Sequences; D014960:X Chromosome
chemical_list: D004251:DNA Transposable Elements; D022041:Euchromatin; D006570:Heterochromatin