Linear connection of condensing chromosomes in nuclei of synchronized CHO cells

Reversibly permeabilized cells allowed the analysis of intermediates of large-scale chomatin condensation in a cell cycle-dependent manner. This paper summarizes major intermediates of chromatin condensation and visualizes connectivity between different forms of chromosomes. At the early S phase the veil-like fibrillary chromatin is supercoiled to form chromatin bodies representing the earliest visible chromosomes. Supercoiling results in a chromatin fiber, which turns to rope (thick fiber) forming loops and chromatin ribbon. The elongated shape of prechromosomes indicates that they are arranged head to tail. Bent forms (loop, c-, and v-shaped structures) of interphase chromosomes open at the end of S phase. Linear arrangement of chromosomes was observed to the end of the condensation process, suggesting that connectivity of chromosomes is maintained throughout the cell cycle.