what is the function of centrosome

 The centrosome, also called the "microtubule organizing center", is an area in the cell where microtubles are produced. Within an animal cell centrosome there is a pair of small organelles, the centrioles, each made up of a ring of nine groups of microtubules. There are three fused microtubules in each group. The two centrioles are arranged such that one is perpendicular to the other.

During animal cell division, the centrosome divides and the centrioles replicate (make new copies). The result is two centrosomes, each with its own pair of centrioles. The two centrosomes move to opposite ends of the nucleus, and from each centrosome, microtubules grow into a "spindle" which is responsible for separating replicated chromosomes into the two daughter cells.

PLANT CELL CENTROSOME: Plant cells have centrosomes that function much like animal cell centrosomes. However, unlike centrosomes in animal cells, they do not have centrioles.

 The centrosome is an organelle that serves as the main microtubule organizing center of the animal cell as well as a regulator of cell-cycle progression.  The centrosome, also called the "microtubule organizing center", is an area in the cell where microtubles are produced. Within an animal cell centrosome there is a pair of small organelles, the centrioles, each made up of a ring of nine groups of microtubules. There are three fused microtubules in each group. The two centrioles are arranged such that one is perpendicular to the other.

During animal cell division, the centrosome divides and the centrioles replicate (make new copies). The result is two centrosomes, each with its own pair of centrioles. The two centrosomes move to opposite ends of the nucleus, and from each centrosome, microtubules grow into a "spindle" which is responsible for separating replicated chromosomes into the two daughter cells.

PLANT CELL CENTROSOME: Plant cells have centrosomes that function much like animal cell centrosomes. However, unlike centrosomes in animal cells, they do not have centrioles.

 The organelle marked no. 13 here is centriole containing centrosomes.

Roles of the centrosome

Centrosomes are often associated with the nuclear membrane during interphase of the cell cycle. In mitosis the nuclear membrane breaks down and the centrosome nucleated microtubules can interact with the chromosomes to build the mitotic spindle.

The mother centriole, the one that was inherited from the mother cell, also has a central role in making cilia and flagella.^[8]

The centrosome is copied only once per cell cycle so that each daughter cell inherits one centrosome, containing two centrioles (see also: centrosome cycle). The centrosome replicates during the S phase of the cell cycle. During the prophase in the process of cell division called mitosis, the centrosomes migrate to opposite poles of the cell. The mitotic spindle then forms between the two centrosomes. Upon division, each daughter cell receives one centrosome. Aberrant numbers of centrosomes in a cell have been associated with cancer. Doubling of a centrosome is similar to DNA replication in two respects: the semiconservative nature of the process and the action of cdk2 as a regulator of the process.^[9] But the processes are essentially different in that centrosome doubling does not occur by template reading and assembly. The mother centriole just aids in the accumulation of materials required for the assembly of the daughter centriole.^[10]

Centrosome (shown by arrow) next to nucleus

In animal cells, centrosomes contain two structures called centrioles. Interestingly, centrioles are not required for the progression of mitosis. When the centrioles are irradiated by a laser, mitosis proceeds normally with a morphologically normal spindle. Moreover, development of the fruit fly Drosophila is largely normal when centrioles are absent due to a mutation in a gene required for their duplication.^[11] In the absence of the centrioles the microtubules of the spindle are focused by motors allowing the formation of a bipolar spindle. Many cells can completely undergo interphase without centrioles.^[8] Unlike centrioles, centrosomes are required for survival of the organism. Acentrosomal cells lack radial arrays of astral microtubules. They are also defective in spindle positioning and in ability to establish a central localization site in cytokinesis. The function of centrosome in this context is hypothesized to ensure the fidelity of cell division because it greatly increases the efficacy. Some cell types arrest in the following cell cycle when centrosomes are absent. This is not a universal phenomenon.

When the nematode C. elegans egg is fertilized the sperm delivers a pair of centrioles. These centrioles will form the centrosomes which will direct the first cell division of the zygote and this will determine its polarity. It is not yet clear whether the role of the centrosome in polarity determination is microtubule dependent or independent.