Sorsa V
J Cell Sci. 1983 Nov;64:255-64. doi: 10.1242/jcs.64.1.255.
Results obtained from the thin-section electron microscopy of salivary gland chromosomes of Drosophila melanogaster mainly support the concept of cable-like organization of polytene chromosomes, with disk-like bands composed of parallel bundles of homologous chromomeres. Outward orientation of loop fibres may generally cause a toroidal bending in the chromomere bundles. Both longitudinal and transverse sections of polytene chromosomes indicate that the bands may contain toroidal subunits. Torus-shaped bands were only found in thin sections of the most distal and most proximal regions, as well as in certain heavy bands at the late-replicating regions of polytenized interphase chromosomes. This suggests that an incomplete duplication of chromomeres may be a reason for torus formation, by preventing the separation of sister chromatids at the earliest phases of the polytenization process. The appearance of more numerous, but smaller, subunits in thin-sectioned faint bands is interpreted as a consequence of more complete segregation of sister chromatids in those bands during polytenization.
从黑腹果蝇唾液腺染色体的超薄切片电子显微镜观察中获得的结果主要支持多线染色体呈索状组织的概念，其盘状带由同源染色粒的平行束组成。环纤维的向外取向通常可能导致染色粒束出现环形弯曲。多线染色体的纵向和横向切片均表明，带可能包含环形亚基。仅在最远端和最近端区域的薄片中，以及在多线化间期染色体的晚复制区域的某些重带中发现了环形带。这表明染色粒的不完全复制可能是形成环的一个原因，这是由于在多线化过程的最早阶段阻止了姐妹染色单体的分离。在薄片中较淡的带中出现更多但更小的亚基，被解释为在多线化过程中这些带中姐妹染色单体更完全分离的结果。
