title: Variations in the number of the Y chromosomal rRNA genes in Drosophila hydei.
abstract: The number of rRNA cistrons is measured by filter saturation hybridization in different stocks of D. hydei, where the wild-type X chromosome has one nucleolus organizer (NO) and wild-type Y has two separated NO's. XX/Y females having no X chromosomal NO show an rDNA content exceeding that of a Y chromosome. An even greater increase in the rRNA cistron number is measured in two translocation stocks where the XX is combined with one half of a Y and, therefore, each stock contains only one of the two Y chromosomal NO's. But when the same Y fragments are brought together with a wild-type X chromosome they lose about one-half of their rRNA cistrons within one generation. Males with two complementary Y fragments but having no X chromosomal NO show a considerably higher rDNA content than the XX/Y females, although both are equal in respect of their NO number. Consideration is given to related phenomena in Drosophila melanogaster.
mesh_terms: D000782:Aneuploidy; D000818:Animals; D002466:Cell Nucleolus; D003433:Crosses, Genetic; D004330:Drosophila; D004331:Drosophila melanogaster; D005796:Genes; D005838:Genotype; D009696:Nucleic Acids / Q000096:biosynthesis; D012335:RNA, Ribosomal; D012730:Sex Chromosomes
chemical_list: D009696:Nucleic Acids; D012335:RNA, Ribosomal