Hey guys, it's Medicosis Perfectionist, where medicine makes perfect sense. Let's continue our biology MCAT playlist. In previous videos, we have talked about the cell cycle.
Today, we'll talk about the M phase, aka mitosis, where one parent cell will give you two identical daughter cells. So, let's get started. Here's the beautiful cell cycle. You can divide it into the interphase, which is G0, G1, S, and G2.
And you have the M phase, which is mitosis. Why do you put the M phase in a separate category? Because this is the only one that has cell division. Doofus.
You can divide the cell cycle into action phases, quote-unquote, and gap phases. The gap phase are G0, G1, and G2. These are for growth.
G for growth. Action phases. In the S phase, we replicate the DNA. But in the M phase, this is the actual mitosis, the actual cell division.
Mitosis. What does osis mean? Osis means a state.
or a condition. What does mite mean? It came from a Greek word, mitos, which means the length of a thread that's used to separate wrap threads.
So, in other words, there is separation. Oh, separation of one parent cell into two identical, beautiful daughter cells. Mitosis versus meiosis.
Mitosis for somatic cells. Meiosis for sex cells, your gonads, your ovaries. or your testicles.
Mitosis is not involved in sexual reproduction, not at all, but meiosis is involved in sexual reproduction, your ovaries and testicles. What is the end result of mitosis? Two deployed cells. So this is the parent cell, was 2N. It has 46 freaking chromosome.
And then the end result of mitosis, you get two new identical cells, and they are deployed, which means they are 2N. identical to the parent cell, but now the parent cell is gone. The parent cell has become two daughter cells. However, in meiosis, you get four haploid, just 1N cells. So here is the parent cell, which was 2N, but now you have four Ns, and of course, the parent is gone.
So the cell cycle is divided into the interphase and the M phase or mitosis. Mitosis itself is subdivided into four phases. Prophase, metaphase, anaphase, and telophase.
For some weird reason, this topic drives students nuts. And the reason why is that they don't get the language. If you understand what these words mean, it becomes a piece of cake. Trust me.
Prophase. Oh yeah, pro means professional. Shut up. This is pro as in pre, before, prior to, earlier, former, in preparation for, in anticipation of, in advance of, ahead of, etc. Sure.
Okay, Metacostas, I got you, I got you. Pro means before. But before what? Before the metaphase.
Metaphase. What does meta mean? Meta means change. If you remember your organic chemistry, here you had the six carbon ring. That position was called the ortho position.
Ortho means straight. Para because it's parallel to the ortho. Look at this.
But meta is change. You don't believe me? There is a condition in medicine called metahemoglobinemia. What does that mean? Hemia means blood.
hemoglobin is the hemoglobin which is in your red blood cell and met means change because your hemoglobin in your blood has been changed from fe2 to fe3 from ferrous to ferric so meta means change next you have the anaphase what does ana mean what does anatomy mean tome means to cut there is the microtome it cuts I had peptic ulcer disease for a very long time, and this was in the 18th century, so the doctor recommended a vagotomy. Tomy means to cut. Vago is the vagus.
Cut the vagus. Tomy means to cut. Anatomy. Tomy, cut. Ana, up.
So anatomy literally means to cut you up. Rhetorically speaking, because I don't want any lawyers'attentions. Telophase. Tilo. Tilo means the end.
For. or the purpose. Telos in Greece is the purpose.
What's your telos in life? And that's why we call it television. Vision means vision to see. Tele means far. Oh, you can watch football games from a stadium that's far away.
Television. Telescope. After telophase, you have the cytokinesis.
Cyto means cell. Kinesis from kinetic to move. So the cell will basically move away from each other. Hashtag cell division.
Pro, meta, ana, telo. Pre, the metaphase, the meta is the change, the ana, up, which means separation, tillo is far, it's the end, it's the end result, it's the purpose of the mitosis, and then cytokinesis, basically separation of the cell into two different cells. So here is your beautiful cell before division, and then prophase. So, yeah, because we are preparing to the metaphase.
It comes before the metaphase. How do you prepare? Okay, you need that centrosome, which contains two centrioles.
And then you need to condense your genetic material into lovely chromosomes. Each one has two sister chromatids joined together in the central centromere. After this metaphase, meta means change.
Look at this, the change of the centrioles. They were together here, but now each one goes to a separate pole of the cell. And look at the alignment of the chromosomes.
Man, it's beautiful. And metaphase has an M. We form mitotic spindle, which are basically microtubules.
Next, anaphase. Ana means up, up. Separates me up into two different sister chromosomes.
One sister here, the other sister there. I'm gonna miss you, sister. Next, the telos, the purpose, the end result.
Now you have a nuclear membrane and another nuclear membrane, and the cells are ready to separate in a process called cytokinesis, movement of the cells. Medicine makes so much sense once you understand what the flip you're talking about. Let's start with the prophase, pro, before the metaphase. Okay, everything here ends in t-i-o-n.
There is condensation of chromatin into chromosomes, i.e. two sister chromatids. with centromere in between. Separation of centriole pairs to opposite side of the cell.
Formation of the mitotic spindle or the spindle apparatus, which are made of microtubules. Dissolution of the nuclear membrane, which was surrounding the nuclear material, aka your chromosomes. Next, you have the metaphase. Meta means change. What change are you talking about?
Basically, it's alignment. Just keep it secret. Everything is aligned, like Hercules when the stars are aligned.
What kind of a woke movie is this? Movement and settlement of centriole pair, as you see, on opposite sides of the cell. So in the prophase, they started moving, but in the metaphase, they have settled and married each other.
Oh, it also started with an M. And then here's the secret word in metaphase, alignment. Metaphase plate formation. Look at the alignment in the center.
This is called the equatorial plate formation because it's in the equator. My totic spindle fibers, which are microtubules, join that centriole here to the centromere here. Next, you have the anaphase. What does ana mean?
Up. Separation. Separate me up. Split each of the centromere that was here in the center by degrading the proteins of the centromere.
And now we have two separate pairs. Separation of the sister chromatids. And then the kinetochore fibers will shorten and you pull the sister chromatid to opposite it.
Poles of the cell. I'm gonna miss you, sis. Okay, Metacosis, but what the flip is the kinetochore?
Okay, here is your centriole, which is at the pole, and then there is the centromere, which is in between. How do they join together? Through the mitotic spindle. But then when the mitotic spindle goes to reach for the centromere, it attaches to a doorknob known as the kinetochore.
It's like an anchor. It's like Anderson Cooper. Next, you have the telophase, the end, the purpose. What's going to happen here?
Basically, the reverse of the prophase. You remember the prophase? Yeah, formation of the mitotic spindle. No, there's disappearance of the mitotic spindle. Oh, because we no longer need them.
Do you remember the prophase? Oh, yeah, it was dissolution of the nuclear membrane. No, in telophase, there's formation of the nuclear membrane because we need to surround the nuclear material of the cell and of this cell. And then you have formation of cleavage, furrows. check your heart.
I'm not making that joke. Where the flip are these cleavage furrows? Look at these.
These, yeah, these two are the cleavage furrows, because the cells are ready to divide from one cell into two new beautiful daughter cells. And then, in prophase, there was coiling and condensation of that genetic material into chromosomes, but now we have uncoiling or relaxation of the chromosomes. They are reverting back to their interphase form before. mitosis. Each one of the two nuclei will contain a complete copy, aka 2N, of the genetic material identical to the parent cell.
Cytokinesis. This is the easiest because the name literally has the answer. Cytokinesis. Cell separation.
Separation of the cytoplasm and organelles into two identical sets, one for each neuron. Why not separation of the nuclear material? Because the nuclear material was separated in the anaphase, doofus. Now test your knowledge. Cell cycle phase.
What cell cycle phase is this? Is this the interphase or the mitosis? It's the mitosis. Which part of mitosis?
This is the prophase. What happens in the prophase? Four things.
Condensation of chromatin into chromosome. Separation of synterial pairs to opposite poles of the cell. Dissolution of the mitotic spindle.
Dissolution of the nuclear membrane. Next question, please pause. Here are the answers. Cell cycle phase, M phase.
Mitosis phase, this is the metaphase, metaphor change. The key word here is alignment in the center. What happens?
M, metaphase. M, movement and settlement. They settle down, they marry onto opposite sides of the cell. And then there is alignment. equatorial plate formation.
Next question, please pause. Cell cycle phase, this is mitosis or M phase. What do you see here? I see separation up anaphase.
What happens in the anaphase? You get split of each centromere into two. Separation of the sister chromatids into opposite sides, and then the kinetochore fibers, which is the kinetochore, which is the doorknob, will connect the centromere with the centriole.
And then we pull those fibers, and you pull the sister chromatids into opposite poles of the cell. Please pause. Cell cycle phase. This is the M phase. Mitosis phase.
Oh, this is the end result. The telos. The purpose.
This is the telophase. It's the exact opposite of the prophase. You have disappearance of the mitotic spindle, formation of nuclear membrane, formation of cleavage furrows, uncoiling and relaxation and decondensation of chromosomes, and and then each one of the two nuclei will contain a complete copy, 2N, of the genetic material. Cell cycle phase, M phase, mitosis phase, this is cytokinesis, just after telophase, what happens? Cytokinesis, cell separation.
Separation of what? Of the nuclear material? Shut up! Separation of the cytoplasm and organelles into two identical, beautiful, new daughter cells.
And here is everything in one slide, pause and review. What's the end result of cell division through mitosis? There is a finite number of division, not infinite, until, normally, apoptosis, a programmed cell death known as cell suicide.
But abnormally, if you have been hit with pathology like ischemia, for example, you get necrosis. This is cell homicide. Always evil.
If you want to take your education to the next level, make a table and compare between the phases. Start by drawing the cell and then tell me what happens. Some pros for the pros.
What are the microtubule organization centers in the body? The centrosome is one, the basal body of cilia and flagella is another one. What the flip are esters? These are anchors protein that anchor the centriole to the cell membrane at opposite poles of the cell. However, the kinetochore is different.
You look at this. This is the centriole trying to attach to the centromere and then there is a small doorknob here. We call it the kinetochore or kinetochore fibers.
Quiz time! What's the difference among kinetochore, kinetoplast, kinetoplasted, and kinetoscope? The answer will be in the next video in this playlist called MCAT Biology. These products are heavily discounted for a very limited time. You can get 119 PDFs about bleeding and coagulation, you can get 50 hematology cases, and for free you can get questions and answers about bleeding and coagulation, and you can get my biology notes for free.
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