caa a22 4500 477090249 CHVBK 20180405111514.0 cr unu---uuuuu 170330e19960301xx s 000 0 eng 10.1007/BF02259705 doi (NATIONALLICENCE)springer-10.1007/BF02259705 Melosis in holocentric chromosomes: Kinetic activity is randomly restricted to the chromatid ends of sex univalents in Graphosoma italicum (Heteroptera) [Elektronische Daten] [José González-García, Carmen Antonio, José Suja, Julio Rufas] We have determined the number and location of the nucleolar organizing regions in spermatocytes ofGraphosoma italicum (2n=12A+ XY♂/XX♀) by means of silver impregnation, chromomycin A3/distamycin A staining and fluorescencein situ hybridization. The identification of only one nucleolar organizing region located at one of the X chromosome ends has provided a suitable cytological marker to analyse the segregation of this univalent and that of the XY pseudobivalent during the first and second meiotic divisions respectively. Our results clearly show that at first meiotic metaphase the chromatids of the X chromosome are orientated with their long axes perpendicular to the polar axis. Although the kinetic activity is restricted to only one end in both X chromatids during the first meiotic division, both ends of the same chromatid have the same probability of showing such kinetic activity. In this sense, we also report that the chromatid segregation maybe initiated either at the same sister chromatid ends or at opposite ends in each chromatid. Thus, this indicates a sex chromatid independence as regards to the chromatid segregation during the first meiotic division. Throughout the second meiotic division both ends of the X chromatid are involved with the same probability in the end-to-end association to conform the XY pseudobivalent. This also implies a random localization of the kinetic activity at the ends opposite to those involved in the end-to-end association. Rapid Science Publishers, 1996 holocentric chromosomes nationallicence chromosome segregation nationallicence meiosis nationallicence sex chromosomes nationallicence González-García José Unidad de Biología Celular, Departamento de Biología, Edificio de Ciencias Biológicas, Universidad Autónoma de Madrid, 28049, Madrid, Spain aut Antonio Carmen Unidad de Biología Celular, Departamento de Biología, Edificio de Ciencias Biológicas, Universidad Autónoma de Madrid, 28049, Madrid, Spain aut Suja José Unidad de Biología Celular, Departamento de Biología, Edificio de Ciencias Biológicas, Universidad Autónoma de Madrid, 28049, Madrid, Spain aut Rufas Julio Unidad de Biología Celular, Departamento de Biología, Edificio de Ciencias Biológicas, Universidad Autónoma de Madrid, 28049, Madrid, Spain aut Chromosome Research Kluwer Academic Publishers 4/2(1996-03-01), 124-132 0967-3849 4:2<124 1996 4 10577 https://doi.org/10.1007/BF02259705 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF02259705 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- González-García José Unidad de Biología Celular, Departamento de Biología, Edificio de Ciencias Biológicas, Universidad Autónoma de Madrid, 28049, Madrid, Spain aut NATIONALLICENCE 700 1- Antonio Carmen Unidad de Biología Celular, Departamento de Biología, Edificio de Ciencias Biológicas, Universidad Autónoma de Madrid, 28049, Madrid, Spain aut NATIONALLICENCE 700 1- Suja José Unidad de Biología Celular, Departamento de Biología, Edificio de Ciencias Biológicas, Universidad Autónoma de Madrid, 28049, Madrid, Spain aut NATIONALLICENCE 700 1- Rufas Julio Unidad de Biología Celular, Departamento de Biología, Edificio de Ciencias Biológicas, Universidad Autónoma de Madrid, 28049, Madrid, Spain aut NATIONALLICENCE 773 0- Chromosome Research Kluwer Academic Publishers 4/2(1996-03-01), 124-132 0967-3849 4:2<124 1996 4 10577 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer