Chromosomes line up at the metaphase plate, under strain from the mitotic shaft. The two sister chromatids of every chromosome are caught by microtubules from inverse shaft posts. In metaphase, the shaft has caught every one of the chromosomes and arranged them at the center of the cell, prepared to separate.
In metaphase (a), the microtubules of the spindle (white) have attached and the chromosomes have lined up on the metaphase plate. During anaphase (b), the sister chromatids are pulled apart and move toward opposite poles of the cell.
