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Centrosome migration

  1. Jan 14, 2010 #1
    Do the centrosomes start moving toward opposite poles of the cell in prophase or prometaphase in mitosis?

    Can anyone tell me if my explanation of mitosis is accurate.

    Interphase - DNA, centrosomes and organelles are replicated.

    Prophase - Chromosomes condense and nuclear envelope begins to dissolve. Spindle apparatus begins to form on centrosomes.
    Prometaphase - Nuclear envelope disappears. Centrosomes begin to migrate toward opposite poles of the cell. Spindle fibers attach to chromatids at their kinetochores.
    Metaphase - Centrosomes have moved to opposite poles of cell. Chromatids align at metaphase plate.
    Anaphase - Spindle fibers begin to shrink and sister chromatids are pulled apart from one another.
    Telophase - Nuclear envelopes begin to form around the new two sets of chromosomes. Spindle apparatus begins to break down.

    Cytokinesis - Cytoplasm is divided into two. Contractile ring of actin forms cleavage furrow and cell begins to divide into 2 daughter cells.
     
  2. jcsd
  3. Jan 14, 2010 #2
    Chromosome migration to the poles of the cell occurs in the Anaphase.

    Everything on your list would be corrected except for your Metaphase. Centrosomes have moved to the centre of the cell. They are right between the poles, so they are currently at the furthest point from the poles until they start getting closer to the pole on the other side. This is called the equitorial plate and it also is when the chromosomes are at their most condensed during mitosis.

    You got your description of the Anaphase correct so I don't understand why you thought that they move to the poles during the Metaphase????

    Something to add to your description of cytokinesis: The contractile ring is of myosin II and actin. (Myosin II is non-muscle). Hydrolysis occurs to ATP and myosin uses this energy to 'slide' or 'constrict' along the actin.
     
  4. Jan 14, 2010 #3

    Ygggdrasil

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    BogMonkey is correct here. The centrosomes (aka microtubule organizing centers) form the spindle poles in animal cells, hence they are at the poles on opposite sides of the cell. The chromosomes are aligned in the center of the cell, so perhaps you are confusing centromere (the point on the chromosome where the kinetochore attaches) with centrosome. (see http://en.wikipedia.org/wiki/Mitosis#Phases_of_cell_cycle_and_mitosis)
     
  5. Jan 14, 2010 #4
    Indeed I have, thanks for the correction. Sorry about that... now that I think about it I don't even think I've ever heard the term 'centrosome' :tongue: I think when I was taking biology we only talked about centrioles. Centrioles come from the centrosomes correct? It's been quite some time since I've taken bio :smile: I've noticed there are a lot of questions that get asked her recently and not a lot of people attempt to answer them quickly.
     
  6. Jan 14, 2010 #5

    Monique

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    The centrioles duplicate in S-phase, they mature into centrosomes and migrate to the opposite sides of the nuclear envelope during prophase. After nuclear envelope breakdown a mitotic spindle is formed, after which the centrosomes are pulled apart during anaphase.

    Generally speaking the centrosomes move an equal distance across the nuclear envelope, until they are opposing each other. There are exceptions where only one centrosome migrates, or where the whole nucleo-centrosomal complex rotates within the cell (allowing for the regulation of mitotic spindle positioning).
     
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