CENTRIOLE

A 'centriole' is a barrel shaped microtubule structure Posttranslational glutamylation of alpha-tubulin, B. Edde, J. Rossier, J.P. Le Caer, E. Desbruyeres, F. Gros & P. Denoulet, , , Science, 1990 found in most eukaryotic cells, though absent in higher plants and fungi.^[1] The walls of each centriole are usually composed of nine triplets of microtubules. Deviations from this include ''Drosophila melanogaster'' embryos, with nine doublets and ''Caenorhabditis elegans'' sperm cells and early embryos, with nine singlets. These make for more stable structures than unmodified tubulin. An associated pair of centrioles, arranged perpendicularly, constitutes the compound structure known as the centrosome. They organize the pericentriolar material (PCM) which plays a role in organizing the mitotic spindle, which in turn helps the cells to divide. The mitotic spindle functions in the chromosomes. Some animal cells are able to divide their chromosomes without centrioles, for instance in female meiosis. Centrioles play a role in the processes of mitosis and in male meiosis. During cell division the centrioles are duplicated, so that there will be a pair for each daughter cell.
In replication, each new paired set of centrioles is composed of the original centriole, plus a newly-made centriole. If the centrioles are used in forming motility organelles, flagella or cilia, the older of the two centrioles, the mother centriole, becomes the basal body which organizes the structure of the organelle.

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Function

References

Function

Centrioles form spindle fibers to separate chromosomes during cell division (mitosis). However, centrioles are not essential for cell division because when broken down with a laser in cells that do not have them, those cells can still divide normally. Centrioles are also believed to organize the pericentrile material along with γ-tubulin to construct the centrosome of the cell, the non-membraneous organelle that anchors the kinetochore and nonkinetochore microtubules during mitosis and meiosis.

References

1. Cilia and the cell cycle?, L.M. Quarmby & J.D.K. Parker, , , J. Cell Biol., 2005