Biology – Replication and division of nuclei and cells | e-Consult

The centrosome is the main microtubule-organizing center (MTOC) in animal cells. It duplicates during interphase and serves as the primary site for the assembly of the mitotic spindle. Each centrosome contains two centrioles, which are involved in spindle formation.

Spindle microtubules are protein filaments that extend from the centrosomes and attach to the chromosomes at the kinetochores. There are three main types of spindle microtubules:

• Kinetochore microtubules: These microtubules attach to the kinetochores of the chromosomes and are responsible for chromosome movement.
• Astral microtubules: These microtubules radiate outwards from the centrosomes and interact with the cell cortex, helping to position the spindle.
• Interpolar microtubules: These microtubules overlap in the middle of the spindle and help to maintain spindle stability.

Chromosome segregation is achieved through the coordinated action of these structures. Kinetochore microtubules exert pulling forces on the chromosomes, moving them towards the poles. Astral microtubules help to ensure the spindle is correctly positioned. Interpolar microtubules provide structural support and prevent the spindle from falling apart. The precise regulation of spindle assembly and microtubule dynamics is crucial for accurate chromosome segregation, preventing aneuploidy (an abnormal number of chromosomes) in the daughter cells. Checkpoint mechanisms ensure that chromosomes are properly attached to the spindle before anaphase begins.