Telophase and Cytokinesis – Mitosis

by Georgina Cornwall, PhD

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    00:00 And then the elongation continues as we move into telophase. I think about 'teloscope', telescope.

    00:08 And separating of those two nuclei. So, now it's time to repack the chromosomes into a nuclear envelopes.

    00:20 During telophase, the goal is to get the new daughter chromosomes into their own nuclei. In which case we need to break down the spindle apparatus in order to create a new nuclear envelope for each of the new daughter nuclei containing daughter chromosomes. And so as those nuclear envelopes form, the chromosomes begin to unwind so that soon after we complete cell division the DNA is available to make proteins and have the cell function as normal cell would. So then we have the organelles dividing between the cells.

    01:01 And this is a pretty important phase. Telophase, we're forming the new nuclear envelopes but now we need to put some of the organelles in each end. We talked about mitochondria having their own DNA.

    01:15 So naturally mitochondria have to replicate themselves also during this process.

    01:20 In order for each cell to have mitochondria, we want to have some ribosomes in each. So on and so forth.

    01:26 So all of those organelles need to divide before we actually have cytokinesis.

    01:34 So, here is sort of a critical point. We've managed to get our way through each of the phases of mitosis.

    01:42 There are some distinct things that happen here. To review, first of all it all makes sense.

    01:48 We have to get the nuclear envelope out of the way. We have to get microtubules in place to pull sister chromatids apart. We have to have microtubules to push the cell longer. And then eventually we break those apart and we put them in new nuclei. We've now got two separate nuclei and mitosis is complete. But, we have one cell membrane still. We've partitioned the contents of the cell, the other organelles. But now it's time to look at actual cell division. Cytokinesis is technically not part of mitosis because mitosis by definition is nuclear division whereas cytokinesis is division of the cytoplasm or division of the cell itself. So during cytokinesis, we're going to see a belt of those fibers that are actin fibers in the cell. The cytoskeletal elements. This is one of those places they come into play. Pinching right down the center of the cell. And because the membrane is very fluid, we can pinch tighter and tighter and tighter. Those actin molecules can contract and eventually pinch off the cell so that we have two separate cells. These are now the daughter cells. But again, mitosis, nuclear divisions. Cytokinesis is division of the cytoplasm. So now that we have our cells divided, I think that you can have a great understanding of the language of chromosomes. That's going to be really important to pay specific attention to. I might take a moment to write those terms down because they are going to come up again when we look at meiosis or the formation of gametes, sperm and eggs.

    03:42 We are also going to be able to describe how chromosomes are packed. Chromatin winds up into tightly formed DNA so that we can move them nice and neatly. I think of that as like winding up balls of yarn so that you don't have to pull the spaghetti apart. And then you are going to be able to diagram each of the phases of mitosis. I don't think it's so important to memorize the steps as it is to draw the cell and think about where things need to be. It's a fluid process. We divide into phases again for landmarks. And then finally, you should really be able to know the difference now and tell someone the difference between mitosis and cytokinesis. Thank you again for taking time to watch this lecture.

    04:32 I look forward to seing you in the future lectures.

    About the Lecture

    The lecture Telophase and Cytokinesis – Mitosis by Georgina Cornwall, PhD is from the course Cell Cycle and Cell Division.

    Included Quiz Questions

    1. 32
    2. 62
    3. 16
    4. 8
    1. S, G2, prophase, metaphase
    2. S, G2, prophase, metaphase, anaphase, telophase
    3. G1, S, G2
    4. S, G2
    5. G1, S
    1. Telophase
    2. Anaphase
    3. Metaphase

    Author of lecture Telophase and Cytokinesis – Mitosis

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD

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