Meiosis I

by Jason Amores Sumpter
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in this video, we're going to introduce the first part of my oh, sis, which is my Oh sis one. And so recall from our previous lesson videos that before my oh sis can even begin The process of interphase needs to occur first. And so notice over here in our image down below on the left hand side were first showing you the interphase needs to occur before my Oh sis can even begin and recall that interphase consists of the G wan, the s and the G two phase. And during the s phase of interphase, that is when the DNA gets synthesized or replicated. And so before my oasis can even begin, interface takes place and the DNA must be replicated. And then at that point, after the G two phase of interface, the cell can enter into my oh, sis one. And what you'll notice about my oh, sis one is that it actually has very similar steps to my toe, sis, in terms of having a pro fes a meta phase and anna phase a tele phase followed by psychokinesis. And so one thing that you'll note is different is that the phases of my ASUs one are all followed by a one. And so notice. Here we have pro phase one Meta phase one and Phase one. Tell a phase one indicating that these are the phases of my ASUs one now recall from our previous lesson videos when we were talking about my toe sis that sometimes the phase pro meta phase which would come between pro fes and Meta phase, is sometimes batch to with the previous phase pro phase one. And so, even though we're not showing you a pro meta phase here in this image, the events of pro meta phase are still taking place in pro phase one. And so really, the events of pro phase one and tell a phase one are going to be very, very similar to the events that occurred in my toe, Sis. And so really my oasis one is gonna be similar to my toes is But my ASUs one is going to differ significantly and both meta phase one as well as Anna Phase one. And so because really it's just met a phase one and anna phase one that differ significantly, really. This is where we're going to put most of our focus and so notice that our image down below has these two phases in blue here to help emphasize that these are really the two phases that differ the most from my toe sis. And so in meta Phase one, Of course, the Eman Meta phase represents the M of the middle. And so in meta Phase one, what's going to happen is that homologous chromosomes are going to pair up and they're going to align themselves in the middle of the self. But they'll align themselves in the middle of the self in two rows. And really, this is the big difference here that these chromosomes are aligning themselves in two rows instead of aligning themselves in one row like what we saw in my toe, sis. And so if we take a look at our image down below at meta phase one, what you'll notice is that in meta Phase one, the homologous chromosomes are pairing up with each other to create two rows and so notice We have one row of chromosomes right here, and the second row of chromosomes is over here. And so they're not all lining up in a single file row. They're lining up in two rows. And that is a big difference between my ASUs one, uh, metta phase one of my ASUs one and meta phase of my toe, sis. Now, during an a phase one of my ASUs one, it's actually the homologous chromosomes that are going to separate from each other, while the Sister Crowe motives themselves remain connected. And this is another big difference between my my ASUs one. And my toast is because during my toe, sis, the sister Crowe motives would separate. But during my ASUs one, the Sister Crowe motives remain connected. And it's actually the homologous chromosomes themselves that are going to be separated. And so when we take a look at Anna, phase one down below right here. Notice that the homologous chromosomes they line up in these pairs here in meta phase one. And then it's the homologous chromosomes that air separated. So notice that this homologous chromosome is separating in this direction on dso Is this one here going towards this end of the cell while this homologous chromosome here is going towards this end of the cell and this one here is going towards this end of the cell And so the homologous chromosomes are separating. But the sister chromatic themselves still remain intact. And so that means that we still have replicated chromosomes here. And so that is going to be a big difference between again my ASUs and, uh, my toe sis. And later in our course, we're going to do a side by side comparison of my oh, sis, and my toast is to help further, uh, to help you guys further differentiate between these two and their similarities as well as their differences. But again, the main, uh, phases that are going to be significantly different. And my, oh, sis are going to be meta phase one and Anna, phase one and again pro phase one and tell a phase one are going to be pretty much the same exact events that occurred during my toe, sis in those same phases. So after tell a phase one, of course you can see here there is going to be the process of psychokinesis and psychokinesis is the division of the cytoplasm splitting the cell into two and so psychokinesis during my oh sis, one is actually going to produce to Hap Lloyd daughter cells and then these two hap Lloyd daughter cells that result right over here can then begin the second half of my oh, sis, which is my ASUs two. And so my oasis to is going to begin with these two cells that air now Hap Lloyd. And so you can see they have half the number of chromosomes in comparison to the very, very beginning. And so noticed that there were originally four chromosomes here in this image. In the beginning, that would be the deployed number for this example. And at the end, each cell only has two chromosomes, which is half of four, meaning that these are going to be hap Lloyd. And so this year really concludes our introduction to my oh sis one and how it differs most significantly from my toe, sis. And we'll be able to get some practice applying these concepts and then talk about my oasis to as we move forward in our course. So I'll see you all in our next video