MITOSIS - DISSOCIABILITY OF ITS EVENTS

This chapter describes some events associated with mitosis, such as condensation of chromosomes, breakdown of the nuclear envelope, microtubule rearrangement, development of trilaminar kinetochore, centrosome–kinetochore interaction, chromatid separation, chromosome movement, and nuclear reformation. It discusses how far these events are dissociable, independent, and inducible. Mitotic division is a multistep process by which the genetic material is equally distributed to two daughter cells. The events that are directly associated with the process of mitosis can be classified in three different series: (1) the processes that take place in the cytoplasm, (2) the events linked with the formation of the mitotic apparatus, and (3) the events taking place within the nucleus and associated with the chromosomes. The dissociability of mitotic events has been successfully approached by the study of cell-cycle mutants and temperature-sensitive (ts) mutants. Three main cell types or organisms used for this purpose include (1) lower eukaryotes, (2) Drosophila, and (3) mammalian cells. Colchicine depolymerizes the microtubules and inhibits polymerization of tubulin, but allows the other mitotic events to proceed. Cytokinesis is inhibited, resulting in the formation of a polyploidy cell or a cell with a number of nuclei formed from single or a group of chromosomes. The effect of this chemical clearly shows that the events associated with the mitotic apparatus are quite independent of other mitotic events. © 1993, Elsevier Science Publishers, B.V.