Mitosis and the spindle assembly checkpoint

Article By:

DeLuca, Jennifer G. Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado.

Last reviewed:2010

DOI:https://doi.org/10.1036/1097-8542.YB100046

Mitosis is the process that produces new cells through the replication and division of existing cells. Multicellular organisms such as humans require mitotic cell division for development and growth, and to continually replenish dying cells. Prior to mitosis, the cellular genetic material (DNA), which is organized into chromosomes, is replicated to produce two sister chromatids that remain joined until late mitosis. During mitosis, each sister chromatid pair (that is, replicated chromosome) aligns at the cell equator. Then, the two sister chromatids are pulled apart, thus forming two daughter chromosomes, and are segregated to opposite sides of the cell. The cell is finally halved, resulting in the production of two identical cells from one. Mitosis must be tightly regulated to ensure that the resulting daughter cells have exactly one copy of each chromosome, because missegregated chromosomes are implicated in the initiation and progression of cancer, as well as in the formation of birth defects in humans. The safety mechanism responsible for monitoring mitotic division is known as the spindle assembly checkpoint (SAC) and has evolved to ensure that chromosome segregation occurs faithfully.

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