Mitotic index

Mitotic index is a measure for the proliferation status of a cell population. It is defined as the ratio between the number of cells in mitosis and the total number of cells. Cells in the cell cycle can be identified using antibodies against the nuclear antigen Ki-67. The mitotic index can be worked out from a slide, even with light microscopy. It is the number of cells containing visible chromosomes divided by the total number of cells in the field of view.

If you administer colchicine or other colchicine-derivative medications (i.e. colcemid) you can arrest the cell cycle at this point leaving the chromosomes in their visible form. Colchicine disrupts the microtubule formation which is necessary for the spindle fibers to separate the chromosomes during anaphase.