Centriole

You don't need to be Editor-In-Chief to add or edit content to WikiDoc. You can begin to add to or edit text on this WikiDoc page by clicking on the edit button at the top of this page. Next enter or edit the information that you would like to appear here. Once you are done editing, scroll down and click the Save page button at the bottom of the page.

(Redirected from Centrioles)

Jump to: navigation, search

Image:Spindle centriole - embryonic brain mouse - TEM.jpg

A centriole showing the nine triplets of microtubules. Transmission electron microscope image.

Image:Centriole-schema.SVG

Schematic of centriole showing microtubule triplets

Image:Centriole3D.png

3-dimensional view of a centriole

A centriole is a barrel shaped organelle^[1] 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.^[1] ^[1] An associated pair of centrioles, arranged perpendicularly, constitutes the compound structure known as the centrosome.^[1]

Function

Centrioles are involved in the organization of the mitotic spindle and in the completion of cytokinesis.^[1]

The position of the centriole determines the position of the nucleus and plays a crucial role in the spatial arrangement of cell organelles. In organisms with flagella and cilia, the position of these organelles is determined by the mother centriole which becomes the basal body. Centrioles are an important part of centrosomes which are involved in organizing microtubules in the cytoplasm. ^[1] ^[1]

The inability of centrioles to properly migrate prior to ciliary assembly has recently been linked to Meckel-Gruber syndrome. Additionally, proper orientation of cilia via centriole positioning towards the posterior of embryonic node cells is critical for establishing left–right asymmetry during mammalian development. ^[1]

Structure of centrioles and mechanism of their duplication

Cells usually contain two complete centrioles. During cell replication, a new centriole will grow from the side of each of the preexisting centrioles. The older of the two centrioles in a pair is called the mother centriole and the younger one is called the daughter centriole. The two centrioles in the centrosome are connected to each other by proteins. The mother centriole has radiating appendages at one (distal) end of its long axis and is attached to the daughter centriole at the other (proximal) end. Each daughter cell formed after cell division will inherit one of these pairs (one older and one newer centriole). Duplication of centrioles starts at the time of the G1/S transition and ends before the onset of mitosis.^[1]