title: The location of the nucleolus organizer regions in Drosophila hydei.
abstract: The positions of the nucleolus organizer regions in metaphase chromosomes of Drosophila hydei were detected by in situ hybridization experiments. In agreement with earlier conclusions the nucleolus of the X chromosome was found to originate in a terminal region of the heterochromatic arm. The Y chromosome contains two nucleolus organizers, one in a terminal postion of the long arm, and the other in the short arm. The implications with respect to the evolution of the Y chromosome are discussed.
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002466:Cell Nucleolus; D002467:Cell Nucleus; D002875:Chromosomes; D004330:Drosophila; D004331:Drosophila melanogaster; D005260:Female; D006570:Heterochromatin; D007814:Larva; D008297:Male; D009693:Nucleic Acid Hybridization; D012335:RNA, Ribosomal; D012730:Sex Chromosomes; D013045:Species Specificity; D013094:Spermatozoa; D014316:Tritium; D014529:Uridine
chemical_list: D006570:Heterochromatin; D012335:RNA, Ribosomal; D014316:Tritium; D014529:Uridine