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I know that a centrosme is composed of two perpendicular centrioles, but the following sentences of Wikipedia confuse me:

Interestingly, centrioles are not required for the progression of mitosis.

Many cells can completely undergo interphase without centrioles.

Unlike centrioles, centrosomes are required for survival of the organism.

If centrosomes are essential then does this doesn't imply that centrioles too are necessary since centrosome is made of two centrioles, if not then what is it made of?

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Reading the specified Wikipedia article about Centrosome, actually explains why centrioles are NOT IMPORTANT for the PROGRESSION OF MITOSIS.

To better understand what wiki meant, let us look at both centrioles & centrosomes.

According to Biology Pages for Centrioles and Centrosomes >>

  • Centrioles are built from a cylindrical array of 9 microtubules, each of which has attached to 2 partial microtubules.
  • The Centrosome
    • is located in the cytoplasm usually close to the nucleus.
    • It consists of two centrioles — oriented at right angles to each other — embedded in a mass of amorphous material containing more than 100 different proteins.
    • It is duplicated during S phase of the cell cycle.
    • Just before mitosis, the two centrosomes move apart until they are on opposite sides of the nucleus.
    • As mitosis proceeds, microtubules grow out from each centrosome with their plus ends growing toward the metaphase plate. These clusters of microtubules are called spindle
      fibers.

So, now we know that during mitosis, the nuclear membrane separates and the centrosome nucleated microtubules (parts of the cytoskeleton) can associate with the chromosomes to fabricate the mitotic spindle.

Understanding the conceptual working of centrosome, the Wikipedia article states >>

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.

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.

Therefore, even in the absence of centriole, centrosomes develop Astral microtubules which just exist amid and quickly before mitosis. Astral microtubules are characterized as any microtubule beginning from the centrosome which does not interface with a kinetochore.

Astral microtubules are not required for the movement of mitosis, but rather they are required to guarantee the devotion of the procedure. The capacity of astral microtubules can be by and large considered as assurance of cell geometry. They are totally required for right situating and introduction of the mitotic spindle assembly, and are in this way required in deciding the cell division site in light of the geometry and extremity of the cells.

An important note from the the Wikipedia article >>

Unlike centrioles, centrosomes are required for survival of the organism. Acentrosomal cells (i.e. cells without centrosomes) lack radial arrays of astral microtubules.

They are also defective in spindle positioning and in ability to establish a central localization site in cytokinesis.

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  • $\begingroup$ so if we irradiate the centrioles then, what is left to be called as centrosome? The only constituents of centrosome are 2 centrioles , if we destroy them with laser, then directly we are destroying the whole centrosome too. $\endgroup$ – JM97 Dec 15 '16 at 11:58
  • $\begingroup$ @JM97 that is not entirely correct. If you read the answer, it says centrosome includes 2 centrioles PLUS 100 different proteins. The only constituents of centrosomes are not centrioles. $\endgroup$ – Imtiaz Raqib Dec 15 '16 at 15:14

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