 There are four stages in mitosis that we're going to look at. And the awesome thing is that these stages are also in meiosis. So the time that you spend now getting this under your belt will be worth it. All right. PMAT, prophase, metaphase, anaphase, and telophase. So I'm going to make a list of the things that are happening in each of these phases. And then what I want you to do is you'll be looking at some images and then we're going to do another animation where you can watch the whole process happening. But I'm just going to make my list to start with. First of all, visualize what does the cell actually look like in interphase. In fact, I think I should make a little interphase note. I'm going to put I for interphase. And the most important thing that I want you to know is that our DNA during interphase is in chromatin form. So don't forget that. We look like this because we had to replicate all that DNA. And you don't want to replicate the log, remember? I love having my toys here to play with. So what do you think one of the first things that's going to happen in prophase? We are going to condense the chromosomes. I guess we could say we're going to condense the chromatin into chromosomes. Tell me, Tru, what do my chromosomes look like in prophase? We started looking like this. Okay, here's a question. Which one is what my prophase chromosomes are going to look like as they get condensed? And how do you know? Pretty pleased with sugar on top. Tell me that you know that they're going to look like this. Not like that because they have sisters because they went through S and replicated their DNA, right? Okay, so we condense our chromosomes. We also dissolve the nuclear envelope. That basically makes the nucleus disappear because the nuclear envelope separates the nucleus from the rest of the cell. We lose, we dissolve the nucleolus. So the nucleolus also disappears. Our chromosomes are condensing and we get some new players that we haven't seen yet. We get basically a whole bunch of cytoskeletal structures. We get microtubules and you'll see what they are going to do. Microtubules and these things called centrioles. Centrioles look like these little barrel things. They look like that at a right angle to each other. The microtubules are like little spindly fibery things like that and they're associated with the centrioles and all together they're called centrosomes. Oh, of course they are. So essentially, here's my centriole, here's my microtubule and the whole thing is a centrosome. Why would we have those? These things, we actually have two of them. So we have two centrosomes that are like developing or becoming obvious in prophase and they start to migrate to the poles. Centrosomes migrate to poles. To the poles, what are the poles? Well, it's just like the earth. The poles are going to be on the ends. So this would be my centriole with its little spindle fibers. So this would be my centrosome and they migrate to the poles. They start out kind of hanging out in the nucleus and then as prophase continues, they migrate to the poles. Metaphase, first, most importantly, the whole thing is a cycle. So having a line at each stage is like really, how do we draw a line at a stage? Because it's going to cycle into the next stage. These microtubules attach to my chromosomes. So look at this. And they actually attach on both sides. They end up with strings attached to each chromosome. And in metaphase, the chromosomes, the sister chromatids, do you agree with that? Sister chromatids are pulled to the metaphase plate. Or the equator of the cell. This is my metaphase plate. So my sister chromatids are like jostled around until they line up nicely in the middle. Metaphase in the middle, that's how I remember. Metaphase. So prophase, we've attached our microtubules. When we start, we attach them to the centromeres of the sister chromatids. Of the sister chromatid team. And are you kind of visualizing like what's going to happen? By the time metaphase is completed, look at this. True story. You will see all the chromosomes lined up in the middle. And we've got these microtubules attached to the sister chromatids. Anaphase, what do you think is going to happen? Kind of makes me want to cry because it's so cool. Anaphase, well, it kind of makes me cry because it's a little bit sad too. The sister chromatids are split. Okay, that part makes me want to cry, but anaphase is like my favorite of all the phases because truly, when you split apart those sisters, their little legs, their little sister chromatid parts, the centromere itself gets split in half. Look at that. They literally, here they were stuck together and then those microtubules shorten and pull the sister chromatids apart to the poles. And in telophase, the story is done. The sisters are at the poles. So if you think about it, at the poles, you're going to have a complete set of chromosomes. What? How cool is that? We now have a complete set of chromosomes at each end and the telophase reverses prophase. So the chromosomes unravel. The nuclear envelope reforms. The nucleolus reforms. The microtubules disappear. So the whole thing is reversed and you end up with a nucleus on each end. The nuclear division, that's all that mitosis is. You just divided your nucleus, but the game isn't over. Do you want a cell with two nuclei? Most of the time, no. So we've got one more stage, one more thing to happen.