Centriole

A centriole in biology is a barrel shaped microtubule structure found in most animal cells and algae though not frequently in plants. The walls of each centriole are usually composed of nine triplets of microtubules, although Drosophila embryos have nine doublets and Caenorhabditis elegans sperm cells and early embryos have nine singlets. An associated pair of centrioles, spatially arranged at right-angles, constitutes the compound structure known to cell biologists as the centrosome. Centrioles are very important in the cell division process. 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.

Structure

A pair of small cylindrical structures that lie next to each other in a T shape, but not touching. The centrioles are constructed of nine microtubule doublets that are arranged together in a star formation, as well as many others.

Function

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