title: Species-specific non-expression of ribosomal RNA genes in a mammalian hybrid, the mule.
abstract: The expression of nucleolus organizer activity in diploid cells was investigated in a model system for mammalian hybrids, the horse-ass cross (mule), by means of sequential Ag-NOR and chromomycin A3/distamycin A-DAPI (CDD) staining in lectin-stimulated peripheral blood lymphocytes (PBL). As a rule we found species-specific non-expression of the horse-derived NOR chromosomes in the mule, whereas the ass-derived NOR chromosomes were active. The results of PBL interphase studies were compatible with the data gained from mitotic metaphase analyses.
mesh_terms: D000818:Animals; D002874:Chromosome Mapping; D004275:DNA, Ribosomal / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D006824:Hybridization, Genetic; D007399:Interphase; D008297:Male; D008677:Metaphase; D009697:Nucleolus Organizer Region / Q000648:ultrastructure*; D010527:Perissodactyla / Q000235:genetics*; D012335:RNA, Ribosomal / Q000096:biosynthesis*; D013045:Species Specificity
chemical_list: D004275:DNA, Ribosomal; D012335:RNA, Ribosomal