title: Cytogenetic analysis of the paternal sex ratio chromosome of Nasonia vitripennis.
abstract: Paternal sex ratio (PSR) is a B chromosome found in the parasitic wasp Nasonia vitripennis. PSR has a unique etiology in that it destroys the paternal chromosomes of fertilized eggs, resulting in the production of all male families. This study examined structural aspects of PSR including size, C-banding, and silver staining. PSR was found to constitute approximately 5.7% of the genome of carrier males. C-banding confirmed the heterochromatic nature of PSR and the data suggest that PSR remains primarily condensed throughout the cell cycle. Examination of prometaphase spermatocytes revealed a secondary constriction on PSR. The constriction, however, did not stain positive for nucleolus organizer activity. During mitosis, PSR and the pericentromeric regions of the A chromosomes displayed a temporal pattern of silver staining, involving dense precipitation of silver prior to metaphase. This reaction is indicative of a protein complex specific to the heterochromatin of these regions. The implications of these findings to the origin of PSR are discussed.
authors.affiliation: Department of Biology, University of Rochester, NY 14627.
authors.forename: K M
authors.initials: KM
authors.lastname: Reed
mesh_terms: D000818:Animals; D002503:Centromere / Q000648:ultrastructure; D002875:Chromosomes / Q000648:ultrastructure; D006570:Heterochromatin / Q000648:ultrastructure; D008297:Male; D009697:Nucleolus Organizer Region / Q000648:ultrastructure; D012744:Sex Ratio; D012834:Silver; D013194:Staining and Labeling; D014863:Wasps / Q000235:genetics*
chemical_list: D006570:Heterochromatin; D012834:Silver