Cell Cycle or Cell division complete lecture Interphase Mitosis and Meiosis

>> YOUR LINK HERE: ___ http://youtube.com/watch?v=NwwcWqL5hhI

This animation shows the cell cycle (interphase, mitosis, and cytokinesis), using easy to follow animations, clear explanations, and helpful analogies. Perfect for any student of Biology interested in learning how cells divide to reproduce! • Video Transcript: • The PURPOSE of the cell cycle is to REPRODUCE cells. So, one cell can copy itself to become two cells! Those two daughter cells are IDENTICAL to the original parent cell (EXACTLY the SAME). Each one can complete its own cell cycle to make copies of itself until you end up with lots of cells! This is needed for growth and is how you went from being one single lonely cell to being made of trillions of cells—that’s how you grew). We also need the cell cycle to replace worn out cells and heal tissue damage! So, it is muy importante! • Alright, so the cell cycle has 3 main parts, Interphase, Mitosis, and Cytokinesis. Let’s begin with Interphase. • Interphase is the part of the cell cycle where the cell is NOT DIVIDING. Think of this as normal cell life. The cell is doing normal cell things: growth, metabolism, and so on. • Also, during Interphase you should notice that the nucleus is intact, and that the cell’s DNA is all stringy, like spaghetti. This stringy, uncoiled form of DNA is known as CHROMATIN. • There is ONE REALLY IMPORTANT THING that the cell does during Interphase that is needed in order to do mitosis (which is the next step): the cell REPLICATES or COPIES its CHROMATIN. Notice that each piece of chromatin is now paired up with its copy. We call these paired up copies SISTER CHROMATIDS. So, now the cell has copies of its DNA. This is critical so that the cell can divide up its DNA into 2 cells and still have them be IDENTICAL TO THE ORIGINAL PARENT CELL. • One final thing I want to make clear, INTERPHASE is NOT PART OF MITOSIS. It happens BEFORE MITOSIS and is especially important because it is where the cell’s DNA is copied. • Now, let’s begin MITOSIS, the process of dividing the cell’s DNA into two identical daughter cells. • Mitosis has 4 phases: Prophase, Metaphase, Anaphase, and Telophase, which you can remember as PMAT. • Anyway, the first phase of MITOSIS is called PROPHASE. • During Prophase, there are a few key events: • 1. Chromatin coils and gets nicely packed to form CHROMOSOMES. So, instead of being like a tangled mess of spaghetti, your DNA is tightly packaged and easier to organize and move around. • 2. The nucleus goes away. It literally DISINTEGRATES. Why? Because it is in the way. The chromosomes are trapped inside the nucleus and can’t get moved to where they need to go, unless the cell gets rid of it—so it does. Bye bye nucleus! • 3. The SPINDLE APPARATUS (a bunch of protein tubes that are used to move your chromosomes around) also forms. • It makes sense that all of these things would happen during Prophase, the beginning of Mitosis, because they are things that NEED TO HAPPEN AT THE BEGINNING. • It’s like moving to a new house—there are some things you do at the beginning of the process… • Just like you need to pack up your stuff before moving to a new house, the cell needs to pack up its chromatin into easily moveable chromosomes. • And just like you need to leave your house to move out of it, the chromosomes need to get out of the nucleus, so it vanishes. Your old house doesn’t vanish—but you get the idea. • Finally, if you’re going to move, it makes sense to have your moving truck ready to go. The moving truck is like the spindle apparatus. Again, it makes sense to have this at the beginning of mitosis. • So, that’s prophase. The rest of the phases will go much quicker. • Metaphase is the next phase. In metaphase, the chromosomes line up down the middle of the cell. Think “M” for middle. This makes the chromosomes easily organized so that they can be evenly divided in half in our next phase—anaphase. • During anaphase, the sister chromatids are separated from one another and pulled to opposite ends of the cell. • Telophase is basically the reverse of prophase. Each newly forming daughter cell is going to start its new life in Interphase, so we have to undo all the MITOSIS stuff that helped the cell to divide. Back to normal cell life. • So, the chromosomes uncoil to form chromatin, the nucleus returns, and the spindle apparatus breaks down because it is no longer needed. • Usually at the same time, the cell completely divides in half, a process called Cytokinesis. • The result is 2 genetically identical daughter cells. • That is the entire cell cycle—interphase, mitosis and cytokinesis. • Photo by Justin Shaifer from Pexels (Guy Wearing Science Shirt) • Photo by Andrea Piacquadio from Pexels (Girl Carrying Box) • Moving truck picture from uhaul.com • Music: https://www.bensound.com

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