Suja J A, de la Torre J, Giménez-Abián J F, García de la Vega C, Rufas J S
Departamento de Biología, Facultad de Ciencias C-XV, Universidad Autónoma de Madrid, Spain.
Genome. 1991 Feb;34(1):19-27. doi: 10.1139/g91-004.
The behaviour of two chromosome structures in silver-stained chromosomes was analyzed through the first meiotic division in spermatocytes of the acridoid species Arcyptera fusca. Results showed that at diakinesis kinetochores and chromatid cores are individualized while they associate in bivalents of metaphase I; only kinetochores and distal core spots associate in the sex chromosome. Metaphase I is characterized by morphological and localization changes of both kinetochores and cores which define the onset of anaphase I. These changes analyzed in both autosomes and in the sex chromosome allow us to distinguish among three different substages in metaphase I spermatocytes. B chromosomes may be present as univalents, bivalents, or trivalents. Metaphase I B univalents are characterized by separated cores except at their distal ends and individualized and flat sister kinetochores. At anaphase I sister kinetochores of lagging B chromatids remain connected through a silver-stained strand. The behaviour of cores and kinetochores of B bivalents is identical with that found in the autosomal bivalents. The differences in the morphology of kinetochores of every chromosome shown by B trivalents at metaphase I may be related to the balanced forces acting on the multivalent. The results show dramatic changes in chromosome organization of bivalents during metaphase I. These changes suggest that chromatid cores are not involved in the maintenance of bivalents. Moreover, the changes in morphology of kinetochores are independent of the stage of meiosis but correlate with the kind of division (amphitelic-syntelic) that chromosomes undergo.
通过对蝗科昆虫深色弧翅蝗精母细胞第一次减数分裂过程中银染染色体上两种染色体结构的行为进行了分析。结果表明，在终变期，动粒和染色单体核心是独立的，而在中期I的二价体中它们相互关联；在性染色体中，只有动粒和远端核心位点相互关联。中期I的特征是动粒和核心的形态和定位发生变化，这标志着后期I的开始。在常染色体和性染色体中分析这些变化，使我们能够区分中期I精母细胞的三个不同亚阶段。B染色体可能以单价体、二价体或三价体的形式存在。中期I的B单价体的特征是核心除远端外是分开的，姐妹动粒是独立且扁平的。在后期I，滞后的B染色单体的姐妹动粒通过一条银染链保持连接。B二价体的核心和动粒的行为与常染色体二价体中的行为相同。中期I时B三价体中每条染色体动粒形态的差异可能与作用于多价体的平衡力有关。结果表明，中期I期间二价体的染色体组织发生了显著变化。这些变化表明染色单体核心不参与二价体的维持。此外，动粒形态的变化与减数分裂阶段无关，但与染色体所经历的分裂类型（双着丝粒-单着丝粒）相关。
