Higher-Order Structure of Metaphase Chromosomes Examined by Scanning Electron Microscopy
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The compaction of a chromatin fiber into a metaphase chromosome involves several steps of distinct condensation mechanisms. The radial loops helical scaffold model seems valid to explain the later steps of the compaction. This model at present is, however, not yet fully complete and the structural nature underlying the occurrence of G-banding, for instance, remains to be explained at the level of higher-order structure. In order to refine the higher-order model, we used Indian muntjac metaphase chromosomes. Chromosomes were prepared by the air-drying method and then retreated by the osmium impregnation technique for scanning electron microscopy (SEM). In the course of the study, we found two different types of SEM images of metaphase chromosomes; one showing a helical configuration and the other a segmented one. Although both types of chromosomes were found to consist of 30 nm chromatin fiber loops, the compaction of fiber loops in the former type appeared rather poor compared to that in the latter. The segmented configuration seemed to exhibit an alternative distribution of the chromatin fiber loop clusters that were differentially condensed. The morphological differences found as two types of SEM images seemed to be caused from the different micro milieu that surrounded each of the metaphase nuclei during the air-drying process. Despite such differences in appearance, every metaphase chromosome seemed to consist of helically condensed sister chromatid fibers.
- 関西学院大学の論文
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関連論文
- Nucleolus Organizer Region Lateral Asymmetry Induced by BUdR Incorporation in Mouse Chromosomes(Cell Biology)
- Higher-Order Structure of Metaphase Chromosomes Examined by Scanning Electron Microscopy