  Reproduction and natural selection are the key elements of life. In order to
reproduce, the genetic material must be doubled, separated and placed into two
new daughter cells, each containing a complete set of chromosomes and
organelles. In mitosis, transition from one process to the next is guided by
intricate surveillance mechanisms, known as the mitotic checkpoints.
Dis-regulation of cell division through checkpoint malfunction can lead to
developmental defects and contribute to the development or progression of
tumors. This review approaches two important mitotic checkpoints, the spindle
assembly checkpoint (SAC) and the spindle position checkpoint (SPOC). The
highly conserved spindle assembly checkpoint (SAC) controls the onset of
anaphase by preventing premature segregation of the sister chromatids of the
duplicated genome, to the spindle poles. In contrast, the spindle position
checkpoint (SPOC), in the budding yeast S. cerevisiae, ensures that during
asymmetric cell division mitotic exit does not occur until the spindle is
properly aligned with the cell polarity axis. Although there are no known
homologs, there is indication that functionally similar checkpoints exist also
in animal cells.
