 Hey everybody, Dr. O here and this is where we're going to talk about a couple of things. I want to start by comparing mitosis and meiosis and then I'm going to cover mitosis in some what depth. I'll have one video where I go even deeper and then I want to talk about how the two pair together to form the human life cycle. So let's start with what mitosis is. Real simply, mitosis you're going to see one round the division where one diploid cell, diploid or two in, meaning that it has two sets of chromosomes like the cells in your body or somatic or body cells. We have 46 chromosomes. After mitosis you're going to have one cell with 46 chromosomes has divided once to form two cells that are also diploid, also having 46 chromosomes. Whereas meiosis what you see here is you start with one cell with 46 chromosomes. They have two rounds of division, meiosis one and meiosis two. So instead of ending with two cells you end with four cells but these four cells are haploid meaning they only have one set of chromosomes. So your body cells are going to undergo mitosis. Your sex cells are going to undergo meiosis because sperm and egg cells are the only cells you want that have one set of chromosomes, only 23. So obviously these two work together to form the human life cycle. Let's go ahead and take a look at that here. So let's start with you as as I go. You're a fertilized egg for about 30 minutes you were a single cell right, this fertilized egg. Then you were two, four, eight, 16 you get the point. So cell division of mitosis turns you into a baby that had a few trillion cells and you continue to grow into develop until you're an adult that's made of somewhere around 37.2 trillion cells. But once you're these 37.2 trillion cells you're not done. You're still maintaining cells all the time. Every time cells die they're going to be replaced. Skin cells, cells lining your GI tract, hair cells, whatever. So cell division and mitosis is what got you to the somatic body cells that you're made of these 37.2 trillion give or take more with me. But then you reach puberty and then meiosis kicks in. So then you, let's say you're the man here on the left, you're going to be producing the male gametes, the sperm. Or if you're the woman on the right, you're going to be producing the female gametes, the egg. So meiosis is going to be where you produce sex cells. And then your sperm or your egg is going to find its counterpart. And now we have a fertilized egg or as I go again. And the next generation, so your offspring started a single cell, become fully formed adults, produce, use meiosis to produce sex cells to form the next generation, et cetera. So I like to call that the human lifecycle, which is the combination of a whole lot of mitosis and then enough meiosis to produce your offspring, right? I have one biological child. So all the sperm, my body's made of all I needed one, right? And my wife needed the one egg. So that's going to be the human lifecycle. Now let's go back and let's look a little bit more deeper into mitosis because meiosis is important, but we don't talk about that much until the last chapter together when we talk about the male and female reproductive tracks. So mitosis is going to be the key right now. So I will go into more detail, but I'm going to give you the awesome 10,000 foot view, which is going to have most the important information you need. So here we see the cell lifecycle. First thing I want you to note, this entire thing is not mitosis. Mitosis is just there in the middle. They call it PMAT, so we'll come back to that. But the cell lifecycle starts with interface. Interface is for the average cell, it's 90% of the cell's time. It's an interface. Think about you don't spend all of your time reproducing, you spend most of the time doing your job, whatever it might be. So about 90% of a typical cell's lifecycle or cell cycle is going to be an interface. Some cells are going to stay in interface forever, cells that don't divide. Think the neurons, these kind of things. Other cells like stem cells are really rapidly dividing cells. They're going to be in interface for a short period of time and then they're going to move on and divide again and divide again. So not all cells are in interface all the time, but the typical cell is going to be in interface about 90% of the time. So what's happening during interface, the cell is doing its job. If it's a liver cell, it's making stuff detoxifying, whatever. So interface is when the cell is doing its job. It's not focusing on division, but it is preparing for division. So during interface, you're going to see the replication of DNA and organelles. So during interface, the cell is not started to divide, but it is preparing to divide. All right, so I already mentioned some cells never leave interface, cells that don't divide, other cells aren't through the very long. So that's interface. Then we go into mitosis. So when I say mitosis, you probably think the division of body cells and that's fine. But the actual definition of mitosis is the division of the nucleus. This is why in microbiology, we don't talk about mitosis because bacteria don't have a nucleus. We call it binary fission there. So here we see mitosis or PMAT, prophase, metaphase, anaphase, and telophase or telophase. So real quick, during prophase, the nucleus disappears. Now, so you have all your genetic material, the chromatin, the DNA has clumped together to form chromosomes and the nucleus has disappeared. So that's going to be prophase. During metaphase, the chromosomes line up at the equator of the cell or the metaphase plate. During anaphase, the chromosomes are pulled apart into two piles. During telophase or telophase, two new nuclei form. So now you have that one egg with two yolks. You have one cell with two nuclei. Then we end the cell cycle with cytokinesis, which is where the one cell actually splits into two. Okay, so we'll cover that in more detail later, but that is differences between mitosis and mitosis. A quick overview here of mitosis and then how the two fit into the human life cycle. I hope this helps. Have a wonderful day. Be blessed.