 Hi everybody, Dr. O here, and this is where we're going to cover myosis. So this early in the course, we don't spend too much time talking about myosis. We will get into the production of sperm and egg way, way later, you know, 27, 28 chappers from now. Right? So real quickly, myosis is like mitosis in that you see cell division and DNA being spread around. But mitosis is one round of division where one diploid cell, one body cell with two sets of chromosomes or 46 chromosomes divides into two diploid cells. So in the end, the two cells are the same as the one they came from. Myosis you're going to see two rounds of division. Notice myosis one and myosis two here, where one cell becomes four. But each of those four new cells are haploid. They're only carrying one set or 23 chromosomes. So myosis is used to produce your sex cells or your gametes, the spermatozoa or sperm or the oocyte egg. All right. Let's start here at the top with S phase. We talked about S phase with mitosis. This is going to be interphase where the cell is not dividing, but it is preparing to divide. So the DNA is going to be duplicated. You're going to make a second set of chromosomes and also second set of organelles like the centrosome you see there. So that's going to be interphase, same as with mitosis. With myosis one, it looks a lot like mitosis. You have prophase, prometaphase, metaphase, anaphase, and then telophase, telophase, and cytokinesis. So it looks the same, but there's a couple of really important things that are happening here. During prophase one, we have what's called synapsis where these chromosomes are going to be connected. The sister chromosomes are going to be connected to one another, and that leads to crossing over or a swapping of genes. So let me take a little closer picture here. So notice here on the right hand side, you see, instead of just having, let's say the blue chromosomes are for mom, so you have, this is chromosome one, let's say, you've got mom's copy from her mom, mom's copy from her dad. That is for dad, dad's copy from his mom, dad's copy from his dad. So instead of just having them spread that way, when they come together, there's this process called crossing over. So look at the right hand side. We have a fully blue one, which we say, let's say it came from mom's mom. On the far right, we have a fully red one, which say it came from dad's dad, whatever. But then you see there in the middle, one that's mainly red with some blue, and one that's mainly blue with some red. So as your genes swap over, that's why you get this unbelievable combination of different combinations of genes. So I always like to say that you aren't a combination of your parents gene. Genes, you are a special combination of your four grandparents genes because of this crossing over process. So during pro phase one, the key thing that happens there is this crossing over. So you're getting part of your mom's mom's chromosome and part of your mom's dad chromosome, hopefully that makes sense. That's called crossing over. The other key thing that happens here is during metaphase one, we have what's called random assortment. So as these, because you're only seeing a couple chromosomes in here, but we have 23 sets of chromosomes in ourselves. So these 23 chromosomes are going to line up randomly. And because of that, since we have 23 sets of chromosomes that could randomly line up in any order, you have 8,388,608 different ways that the chromosomes could line up during this process. Which means that the odds that the sperm and egg that made you were the ones that made you are astronomically high, right? It's very special that you're here. There are lots of combinations of humans that could have came from your mom and dad that don't exist because you do. That's awesome. All right, so that's going to be during myosis one, those are the key things that are happening there. I already showed you this, this crossing over being very important. So crossing over and random assortment are the two key reasons that you have so many unique sperm or so many unique eggs or your parents did whatever. The third thing that makes it so random that you're you instead of some other combination besides the crossing over and random assortment is which sperm reached which egg, right? If a different sperm reached that egg or your mother got pregnant a month later with a different egg, you wouldn't be here because of these unique combinations. Then we just have myosis two, again, just looks like mitosis, pro phase two, pro metaphase two, metaphase two, anaphase two, telophase two, and then cytokinesis again. And here we end with four cells that are haploid with one set of chromosomes instead of the diploid cells with mitosis. So each of those four cells, though look at the colors, the blue and the red, the mismatches there, each of those four cells is a unique combination of your mom's mom's DNA and your dad's dad's DNA or your dad's dad's DNA. So what else about that? So with sperm, we'll learn about this later, but with sperm production, all four of these would be sperm when the process is complete. With egg, only one of them is going to be an oocyte. The other three would be called polar bodies and they would be, they would be broken down because you only need one egg at a time. You need millions and millions of sperm in order for fertilization to take place. Okay, so that's meiosis, at least at the level you need to know it. I hope this helps. Have a wonderful day. Be blessed.