Prometaphase, Metaphase and Anaphase – Mitosis

by Georgina Cornwall, PhD

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    00:00 And then we are able to move into; Keep in mind these aren't one phase, the next phase, the next phase.

    00:07 It's a very dynamic process. We've just sort of divided them up to make it easy to understand what's happening and describe some landmark events. So in prometaphase, we see a few other things happening as we prepare for cell division. We'll see that the mitotic spindle begins to form.

    00:28 The kinetochore microtubules which come from the centrioles will connect to the kinetochore handles on each of the sister chromatids. And they'll start jostling and moving the chromosomes around getting ready to line them up in the center of the cell for cell division.

    00:49 Then we will see that during metaphase, the kinetochore microtubules finally pull them into place along the central line of the cell.

    01:02 So looking a little more closely at that. We see during metaphase the individual replicated chromosomes with their sister chromatids are paired because they're stuck together by those cohesin proteins. They're paired right on the central line of the cell. The central line of the cell is called the metaphase plate. It doesn't physically actually exist. It's just the central line of the cell.

    01:28 So the metaphase plate is just the area that the chromosomes line up upon. And in addition now we see another set of microtubules. So we have the kinetochore microtubules grabbing onto the handles on the sides of each chromosome and they are getting ready to pull them apart. But in addition these polar microtubules are coming from the poles of the cell and they actually line up on each other and they're polymerized to grow and grow and grow and grow and actually push the cell longer. So you have two things going on. Polar microtubules pushing the cell longer. Kinetochore microtubules attaching to the kinetochore handles on the sister chromatids, getting ready to pop them apart. And that happens when we enter anaphase. So anaphase, as we take a closer look, we'll see that the sister chromatids are separating. Now, we are going to revert to a little language lesson here because it is really important to note that these are no longer considered sister chromatids. Chromatids are only chromatids when they are attached to each other with those cohesin proteins right at the centromere.

    02:44 Once they become unattached during anaphase, they are now daughter chromosomes. They're chromosomes of their own device now. So their going to be packaged into their own cells. So they are full on adult chromosomes. Let's think of it that way. So, a little closer look at the details here. We see that the cohesin proteins break down. The sister chromatids are able to pull apart. The kinetochores pull them longer. The polar microtubules push the cell longer. Kinetochore microtubules are shortening pulling the sister chromatids which are not sister chromatids anymore. They are daughter chromosomes.

    03:27 Pulling them to the poles of the cell. Now the poles are going to pull apart in anaphase.

    03:34 They are moving apart from each other so we'll see elongation of the cell.

    About the Lecture

    The lecture Prometaphase, Metaphase and Anaphase – Mitosis by Georgina Cornwall, PhD is from the course Cell Cycle and Cell Division.

    Included Quiz Questions

    1. Anaphase — formation of spindle
    2. Prometaphase — mitotic spindle formation
    3. Cohesion proteins — regulate the separation of sister chromatids during cell division
    4. Polar microtubules — determination of cell geometry during cell division
    5. Kinetochores — proteins attached to the centromere of the chromosome
    1. The daughter chromosomes get separated and move towards the poles of the dividing cell.
    2. The sister chromosomes get aligned together on the metaphase plate.
    3. The non-homologous chromosomes get aligned on the one pole of the dividing cell.
    4. The maternal and paternal chromosomes get aligned on the metaphase plate.
    5. The homologous chromosomes move together towards the metaphase plate.

    Author of lecture Prometaphase, Metaphase and Anaphase – Mitosis

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD

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