Centrosomes & Mitotic Spindles

by Jason Amores Sumpter
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in this video, we're going to briefly introduce Sentras, OEMs and my topic spindles. And so recall from our last lesson video that during the S sub phase of interphase, it's characterized by DNA synthesis where the cells going to replicate their DNA. But they also replicate another structure called the central zone. And so the central zone is not to be confused with the Centrum ear, which again is the waste position of a replicated chromosome where the two Sister Crowe motives come together. The central zone is different than the central near the central zone. It is a cytoplasmic protein complex that forms or organizes what are known as the might. Ah, tick spindle on the my tonic spindle is very, very important for my toe sis, which occurs, uh, of course, during the m phase of the cell cycle. And so the my tonic spindle is really just micro tubules proteins of the site of skeleton that coordinates division of the chromosomes, essentially dividing the DNA into the two daughter cells. And so here what we're saying is that in our example images that the central zone is going to be replicated in the S phase and the central zone is ultimately going to be responsible for forming the Mitic spindle during my toe. Sis and Soe, over here in this image, down below notice. Over here on the left, we're showing you a single cell that has Onley one center zone Noticed that a single centrism actually consists of these two smaller proteins here. And so we have one single centrism right here. And we have the nucleus of the cell. Um, within the nucleus, we have these Unruh replicated, uh, chromosomes. And so notice that after the s phase, remember, the S phase is the sub phase of interphase where DNA synthesis is going to occur DNA replication. But in addition to DNA replication, the central zone is also going to be replicated. And so notice that the central zone is replicated. Now there are two centrism. There was one over here, and now there's a second centrism over here. And so we have these central zones here. But also in addition to the centrism is being replicated. Of course, the DNA is going toe also be replicated. So we convert the unrepresented chromosomes here into replicated chromosomes. Notice they each we have this thes x shaped chromosomes here indicating that they are replicated. Whereas over here they're not X shape. They are mawr linear like what you see here. And so really, that is the main point here. And ultimately these centers owns again are going to be very important during mitosis because during my toe, sis, they're going to form what are known as the my tonic spindle. And so here you can see the might attic spindle are these structures that air projecting off of the centrism and they're forming thes micro tubules that are gonna be important for ultimately moving the DNA around in splitting the division of the chromosomes dividing the chromosomes. And again, this will make the central zones and the my tonic spindle are going to be mawr relevant once we start talking about my toe sis a little bit later in our course. So this is a little bit of foreshadowing here for what you are going to see as we move forward. And so this here concludes our brief introduction to center zones and the Mitya Dick spindles, and we'll be able to get some practice as we move forward in our course. So I'll see you all in our next video