 Hello everyone. It's time for us to start talking about the process of mitosis in the cell cycle. Every single cell in our body undergoes a cell cycle and subsequently the process of mitosis. Within the cell cycle, we first have four phases. The first phase is known as the G1 or GAP1 phase. The second phase is known as the synthesis phase or the S phase. The third phase is known as the GAP2 or G2 and then the final phase is known as mitosis. In the GAP1 phase, the cell basically stops and checks to make sure that the cell is ready to undergo the synthesis phase. In the synthesis phase, the cell replicates DNA, so you go from having one copy of DNA to two copies of DNA. This is crucial for the process of mitosis because what's going to happen is you're going to have one copy of DNA will go to one daughter cell and a second copy of DNA will go to the other daughter cell that's produced by mitosis. The G2 or the GAP2 phase is used by the cell to make sure that everything is ready to undergo mitosis and then finally we have the process of mitosis or the M phase. Let's break down mitosis and look at the different phases within mitosis. The first phase of mitosis is known as prophase. Now in prophase, what happens in our cell is that the nuclear membrane dissolves and the chromosomes start to tightly coil so we can actually see them. If you've ever seen pictures of chromosomes, a lot of times what you see is them tightly coiled and you see an X. Now this X is made up of two copies of DNA and they're identical. This is one copy here and this is the second copy here. These were made during the process of synthesis. Let's look at a cell with four different chromosomes. The next step in mitosis is metaphase. Now in metaphase what happens is our chromosomes line up on the equator and they start to get ready to divide. We also have spindle fibers which have connected themselves each to one copy of every chromosome. The next phase is when the chromosomes start to get pulled apart by these spindle fibers. So the spindle fibers are pulling them apart to the different poles. This is known as anaphase. And then finally we have telophase. Now in telophase the chromosomes get pulled to completely apart to the different poles by the spindle fibers and then the cell gets ready to undergo the process of cytokinesis. This is where the cell actually splits and goes from one cell to two daughter cells. The key to mitosis is the fact that the two daughter cells are completely identical to the initial cell that you started with. You start with four chromosomes. Granted there are two identical copies of each chromosome but four different chromosomes in your first cell. And what you end up with are two daughter cells with four chromosomes at the end. That's key. If you've ever cut yourself, if you're a body on a regular basis, always uses mitosis to produce blood cells. Your body uses mitosis all the time. And the idea is that you want to end up with cells that are identical to the ones you start with. So again if you cut yourself your body has to heal and it uses a process of mitosis, blood cells are made every single day and you want them identical to the cells, the parent cells so you use the process of mitosis. So that's one good reason that we should care about mitosis but what's another one? Well unfortunately many people are all too familiar with the process of cancer. Cancer is basically mitosis gone awry. It's mitosis where it just doesn't stop. Mitosis despite what it may seem is actually a very carefully controlled and regulated process. There are actually genes and proteins and such that inhibit mitosis and keep it from happening until it's needed. You don't want your body just producing cells left and right if you don't need them. But what happens with cancer is you get a mutation in some of these genes and it doesn't suppress the process of mitosis anymore. So you start getting a buildup of more cells and more cells and more cells and more cells and these are cancer cells and ultimately this can be fatal. So a simple mutation or buildup of simple mutations can actually cause mitosis to no longer be able to control itself and it just goes crazy and makes too many cells. Hopefully this has given you a good idea as far as why we should care about mitosis as well as a good rundown of the cell cycle and the different stages that are involved. Our next lecture will involve the process of meiosis which is a complementary process that's also incredibly important to our survival.