Mitotic spindle

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Image:Mitotic spindle color micrograph.gif

The mitotic spindle is a structure of the eukaryotic cytoskeleton involved in mitosis and meiosis, often referred to as the meiotic spindle during meiosis. It consists of a bundle of microtubules joined at the ends but spread out in the middle, vaguely ellipsoid in shape. In the wide middle portion, known as the spindle midzone, antiparallel microtubules are bundled by kinesins. At the pointed ends, known as spindle poles, microtubules are nucleated by the centrosomes.

During spindle assembly in mitosis, some of the spindle's microtubules attach to the kinetochores that assemble on the centromere portion of the chromosomes. The chromosomes are pulled into alignment along the spindle midzone to form the metaphase spindle. Once all the chromosomes are aligned with sister chromatids pointing to opposite ends of the spindle, the cell enters anaphase, in which the chromatids separate and move toward their respective poles. Since the center of the spindle specifies the plane along which the cell will divide during cytokinesis, this ensures that each daughter cell will receive one of each chromatid.

The mitotic spindle will not form without Lamin B, a key component of the spindle matrix helping microtubule assembly (Science 31 March 2006: Vol. 311. no. 5769, pp. 1887 - 1893 DOI: 10.1126/science.1122771)de:Spindelapparat nl:Spoelfiguur ru:Веретено деления sk:Deliace vretienko zh:纺锤体