Understanding the Purpose and Function of Centrioles
So, what are centrioles? These cylindrical structures are made up of microtubule groups that are arranged in a pattern of 9+3. They are not formed in plant cells, but are formed in animal cells. In the interphase of mitosis, centrioles replicate. During cell division, they assist in organizing microtubule assembly. It is believed that they are very important in decreasing errors that are possible during mitosis.
Resting and Cell Division
Centrioles are found close to the nucleus. When a cell is not in the process of division, a well-defined centriole is not seen. You will see a centrosome, or a darker and condensed area of the cytoplasm. When cell division is ready to go, the centrioles will seem like they are making their way to the other end of the nucleus. Four centrioles will be present during cell division. They are split into pairs and each pair moves in each direction.
When the cell is resting, it is known as interphase. The centrioles will duplicate when the cell is ready to divide. A mitotic spindle of threads makes itself apparent and the centrioles make their way to the other end of the nucleus during prophase. The chromosomes are now apparent and the mitotic threads connect to the chromosomes. The chromosomes then split and are pulled in the direction of each individual centriole, during anaphase. The entire cell then starts to split during telophase. Then, new nuclear envelopes present themselves after chromosomes start to unravel. Once this is all complete, the centrioles have completed their job.
As part of a centrosome, centrioles play a very important part in cellular organization, especially in microtubule organization within the cytoplasm and the cell's spatial arrangement. The centrioles' position also determines the nucleus' position. The mother centriole determines flagella and cilia position within organisms that have these organelles. The mother centriole will turn into the organism's basal body. When a cell, with the help of centrioles, is not successful in making functional flagella and cilia, it has been found to be related to a variety of genetic and developmental diseases.
It was once thought that centrioles were necessary for the mitotic spindle to form. However, recent studies have shown this is not actually necessary. It has been shown that mutant flies are able to normally develop without a centriole. However, since these mutant flies have no centriole, they are unable to develop flagella or cilia, so this does show that centrioles remain important in these organelles forming.
Stein Carter, J. (1996). Cells and Organelles. Retrieved on February 25, 2011 from University of Cincinnati Clermont College: http://biology.clc.uc.edu/courses/bio104/cells.htm
Davidson, M.W. (2010). Centrioles. Retrieved on February 25, 2011 from Florida State University: http://micro.magnet.fsu.edu/cells/centrioles/centrioles.html