The role of sister chromatid cohesiveness and structure in meiotic behaviour |
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Authors: | J F Giménez-Abián D J Clarke C García de la Vega G Giménez-Martín |
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Institution: | (1) Centro de Investigaciones Biológicas, CSIC, Velázquez 144, E-28006, Madrid, Spain, ES;(2) The Scripps Research Institute, MB-7, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA, US;(3) Facultad de Biología, Universidad Autónoma, Canto Blanco, Madrid, Spain, ES |
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Abstract: | Sister chromatid cores, kinetochores and the connecting strand between sister kinetochores were differentially silver stained
to analyse the behaviour of these structures during meiosis in normal and two spontaneous desynaptic individuals of Chorthippus jucundus (Orthoptera). In these desynaptic individuals most of the chromosomes appear as univalents and orient equationally in the
first meiotic division. Despite this abnormal segregation pattern, the changes in chromosome structure follow the same timing
as in normal individuals and seem to be strictly phase dependent. Chromosomes in the first prometaphase have associated sister
kinetochores and sister chromatid cores that lie in the chromosome midline; we propose that this promotes the initial monopolar
orientation of chromosomes. However, the requirements of tension for stable attachment to the spindle force the autosomal
univalents to acquire amphitelic orientation. Sister kinetochores behave in a chromosome orientation-dependent manner and,
in the first metaphase, they appear to be interconnected by a strand that can be detected by silver impregnation, as seen
in the second metaphase of wild-type individuals. The disappearance of the sister kinetochore-connecting strand, needed for
equational chromatid segregation, however, can only take place in the second meiotic division. This connecting strand is ultimately
responsible for the inability of chromosomes to segregate sister chromatids in the first anaphase.
Received: 25 March 1997; in revised form: 14 July 1997 / Accepted: 22 August 1997 |
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