What is a centriole? Definition:
centrioles are cylindrical cell organelles from the protein tubulin. During cell division, a pair of centrioles each form the centromere from which the spindle apparatus is formed. The microtubule spindle apparatus then separates the chromatids and pulls them to the cell poles. Thus, the centrioles have an indispensable function in both meiosis and mitosis.
Construction of the centrioles
Centriole are cylindrical structures of nine microtubule triplets. They are about 0.3 microns (microns) long and have a diameter of 0.1 microns. For comparison: An euzyte reaches a size of up to 50 μm.
Each triplet consists of a fully developed microtubule (A-subfiber), which is fused with two incomplete crescent-shaped microtubules (B and C subfiber). Nine of these triplets are linked by proteins and form the typical wall of the centriol in the 9x3 structure (see picture). This cross-linking is responsible for the high stability of the centriole.
Centriole usually occur in pairs, where they are arranged at 90 ° to each other. Both centrioles together with the surrounding proteins (pericentric matrix) form the so-called microtubule organization center (MTOC). This controls the number, the polar orientation and the organization of the microtubules during cell division and also coordinates the formation of new microtubules.
Function of the centrioles
Centrioles are mainly important for the removal of the spindle apparatus during mitosis and meiosis. The spindle apparatus is necessary to distribute the chromosomes to the two ends of the cell before cell division (see picture), so that after cell division each cell has a complete set of chromosomes.