<P> The microtubule - organizing center (MTOC) is a structure found in eukaryotic cells from which microtubules emerge . MTOCs have two main functions: the organization of eukaryotic flagella and cilia and the organization of the mitotic and meiotic spindle apparatus, which separate the chromosomes during cell division . The MTOC is a major site of microtubule nucleation and can be visualized in cells by immunohistochemical detection of γ - tubulin . The morphological characteristics of MTOCs vary between the different phyla and kingdoms . In animals, the two most important types of MTOCs are the basal bodies associated with cilia and the centrosome associated with spindle formation . </P> <P> Microtubule - organizing centers function as the site where microtubule formation begins, as well as a location where free - ends of microtubules attract to . Within the cells, microtubule - organizing centers can take on many different forms . An array of microtubules can arrange themselves in a pinwheel structure to form the basal bodies, which can lead to the formation of microtubule arrays in the cytoplasm or the 9 + 2 axoneme . Other arrangements range from fungi spindle pole bodies to the eukaryotic chromosomal kinetochores (flat, laminated plaques). MTOCs can be freely dispersed throughout the cytoplasm or centrally localized as foci . The most notable MTOCs are the centrosome at interphase and the mitotic spindle poles . </P>

The ____ is often called the microtubule organizing center