title: Localization of the lampbrush loop pair Nooses on the Y chromosome of Drosophila hydei by fluorescence in situ hybridization.
abstract: We have used fluorescence in situ hybridization to map the positions of the different repetitive DNA sequences from the region forming the lampbrush loop pair Nooses on the Y chromosome of Drosophila hydei. This region harbours a megabase cluster of tandemly organized repeats of the Y-specific ay1 family and a megabase cluster of tandem repeats of the related Y-specific YsI family. In addition, ay1 repeats also occur in short blocks that are interspersed by other repetitive DNA sequences that we call Y-associated, since they have additional copies on other chromosomes. Using specific probes for ay1, YsI and Y-associated DNA sequences, we show that there is one large proximal cluster of YsI repeats and one, more distally located, large cluster of ay1 repeats. The Y-chromosomal copies of the Y-associated sequences are located in the most distal part of the ay1 cluster. This is consistent with the juxtaposition of ay1 and Y-associated sequences in more than 300 kb of cloned genomic DNA. Since both ay1 and Y-associated sequences have been shown to be transcribed in the Nooses, the lampbrush loop is formed in a distal region of the short arm of the Y chromosome, adjacent to the terminally located nucleolus organizer region. The clusters of homogeneous ay1 and YsI repeats are of no functional significance for the formation of the lampbrush loop.
authors.affiliation: Department of Molecular and Developmental Genetics, Faculty of Sciences, Catholic University of Nijmegen, The Netherlands.
authors.forename: R
authors.initials: R
authors.lastname: Hochstenbach
authors.forename: M
authors.initials: M
authors.lastname: Wilbrink
authors.forename: R
authors.initials: R
authors.lastname: Suijkerbuijk
authors.forename: W
authors.initials: W
authors.lastname: Hennig
mesh_terms: D000818:Animals; D004247:DNA / Q000235:genetics*; D004330:Drosophila / Q000235:genetics*; D017344:Genes, Insect / Q000235:genetics; D017404:In Situ Hybridization, Fluorescence; D007399:Interphase / Q000235:genetics; D008297:Male; D008938:Mitosis / Q000235:genetics; D009690:Nucleic Acid Conformation; D012091:Repetitive Sequences, Nucleic Acid; D014998:Y Chromosome / Q000737:chemistry*
chemical_list: D004247:DNA