Aster (cell biology)

An aster is a cellular structure shaped like a star, formed around each centrosome during mitosis in an animal cell. Astral rays, composed of microtubules, radiate from the centrosphere and look like a cloud. It is one of the variants of microtubules like kinetochore- and interpolar microtubules.

During mitosis, there are four stages of cell division: Prophase, Metaphase, Anaphase, and Telophase. During prophase, two aster-covered centrosomes migrate to opposite sides of the nucleus in preparation of mitotic spindle formation. During metaphase, the kinetochore microtubules connect to the centromere. Afterwards, during anaphase, the kinetochore microtubules pull the chromatids apart into its individual chromosomes and pull them towards the centrosomes, located at opposite ends of the cell. This allows the cell to divide properly with each daughter cell containing full replicas of chromosomes. In some cells, the positions of the asters determine the site of cell divisions.

See also

• Astral microtubules
• Mitosis