 Alright darlings in typical rig style. I have no idea what is gonna happen in this PowerPoint I have no idea I can't remember anything, but I think That we're gonna get a little bit it looks like we're headed in for a little bit of review of our chromosomes and Then I do know that somewhere in here. We're gonna get to watch the whole process of Mitosis take place first thing it's probably a good idea to see how I am Representing the chromatin loosely wound and the chromosomes tightly wound. I think we should probably do some some anatomy in this illustration we're going to have the sperm parent in green and the egg parent in blue and The distinction in color is not super strong But I think there's enough of a difference that as long as you remember that we have All the DNA all the chromosomes that we're going to deal with from the sperm parent are going to be Colored differently than all the chromosomes that are coming from the egg parent When we wind them up when we wind that chromosome that DNA up with those histone proteins then we get the The condensed version which again, I've shown a diagrammatic view of this. I Wish I would have asked you to tell me what those chromosomes are They they look identical. Do you agree with that? They're like they they're the same shape They're the same size the centromeres in the same location One came from sperm one came from egg Those are homologous chromosomes and You have 23 pairs. Do you think that I am going to show? 23 pairs of homologous chromosomes Good gracious. I hope not Because I had to like build all these things But we know that they're there and we could do all of them because we have this karyotype That would let us Okay, we remember that right You're golden Looks like I did four different chromosomes. Oh Look, and I just I see that I shouldn't have said that out loud because that is how many homologous pairs we see And it was a question and that was really good and I love questions that make you Think about it, but I'm not starting this over because it's already three minutes in. All right, so how many okay? I told you that there are four pairs of homologous chromosomes. Can you identify them? Match up the homologs. Can you do that push pause if you need to? Let's see if I do it for you Do you agree? That's the first homolog That's the second homolog You totally got this didn't you and the fourth homolog so there are four pairs of Chromosomes in this in this Illustration we would have 23 we would have 23 different shaped chromosomes. So you know why I didn't make that This is interesting and I didn't talk about this before but This is going to be an important thing when we start talking about heredity When this is our haploid number so N represents the number of chromosomes the number of different chromosomes found in this organism This organism has four different chromosomes. So the haploid number is four The diploid number is going to be eight because there's actually a total of eight chromosomes there. Ah Look How many total chromosomes do you see guys? That's eight and that's our diploid number. Look why didn't I label it the diploid number? What is our diploid number? 46 what is our haploid number? 23 okay, good job What would these look like? Okay? What would it all look like if it was in chromatin form loose chromatin form is let's modify that slightly What okay? Imagine are you ready? loose chromatin form Is that what you imagined I think that actually is the like eight I Don't know it doesn't really look like that's eight tangles, but Maybe okay cell cycle we're good, right you remember the cell cycle Looks like we're gonna do n equals three So we're gonna use three of those chromosomes that I showed you in the earlier thing We're gonna use three different ones, but we're diploid. So we're gonna have We're gonna have six chromosomes that we're gonna deal with In G1 The chromosomes look like this. Do you agree? That we know in interphase our DNA is all in chromatin form so G1 with Three chromosomes, but really there's six in there, right because this is a diploid critter Let's peek if you had to predict what those chromosomes would look like if we wound them up because in That state I dropped my yarn, but in that state They all look like this But if you wind them up and we can if you wind them up This works, right? This is what they would look like if you wound them up and can you identify your homologues They're numbered the number ones are homologues and the twos are homologues and the threes are homologues But that's six pieces of DNA that are in that tangle during G1 Okay During s we're still in the tangle But let's just peek at the chromosomes in the beginning at the beginning of s. What are the chromosomes gonna look like? Just like they looked in G1 This is the beginning of s What's gonna happen during s? The DNA is gonna get replicated. So what are these guys gonna look like at the end of s? Let's see. Oh, that's what it really looks like. Okay, awesome What does it look like at the end? It still looks like that But tell me we're gonna peek at the chromosomes Have you predicted? Yes We now have sister chromatids. Can you identify your sisters? Each sister is attached at the centromere. You see your centromere in there and The sisters are attached to each other at the centromeres We have twice as much DNA. That's at the end of s Okay Time out. Oh my gosh, I'm such a oh, that's a technical foul You didn't get a technical foul unless you don't do this task Label these chromosomes. I want you to label sister chromatids the centromeres the homologous Chromosomes and tell me what the haploid number is Dude, I have no idea how I'm gonna give you the answer. So you got to push pause and do those things and Then because who knows what's coming next What did we did we didn't get an answer? Well, I really want to see the answer But you know the answer already because we've done it like a hundred times So I think we're good. Maybe the only thing that I'd want to say is that each centromere represents an entire chromosome So you have two sisters Attached at a centromere, but that's one chromosome So the chromosomes are bigger than they used to be but they still it's still just one chromosome Okay, but I think everything else is Straightforward yes, and our haploid number in this case is three still okay But in G2 What it looks like awesome Good thing for copy and paste is all I have to say If we were to peek at the chromosomes predict, what's it gonna look like? The same as it did at the end of S We just have doubled our DNA and all the sisters are attached at centromeres Okay, shall we see what happens in mitosis? Let's watch Okay, we have a cell do you see my cell my nuclear envelope Do you see my centrioles and the nucleolus? Yes, we see all the parts and you see the chromatin So we're about to start mitosis. What's the first stage of mitosis? Prophase so let's see. Oh, what why do we have to do in why do we have to do we just did interface? All right, fine. We'll do interface first G1. Yeah. Yeah. Yeah, that works for okay. I see what I'm doing here S at the beginning are we gonna peek at S in the beginning S in the end That's cool because we can see that the DNA actually doubled. That's cool Okay, should we peek at the chromosomes? Peeking at the chromosomes. This is what they look like awesome G2. Yeah. Yeah. Yeah, whatever. Okay Now we're gonna go into prophase. Yes Yes, but why did our cell disappear? I Don't know that was an extra slide. What's gonna happen in prophase? When I whisper I should whisper right into the microphone What's gonna happen in prophase? Did you predict that? Look at the nuclear envelope is disappearing and a chromosome condensed Okay, they don't condense like this But there's no planet on which I am going to condense them any different What else do you notice is happening? We're condensing our chromosomes. What's happening to the nucleolus? I don't know if you can tell this is very effective animation technique The nucleolus is getting lighter fainter because it's disappearing So is the nuclear envelope. It is also disappearing Who is migrating? Dude, we got some migration going on Look, we've got our spindle fibers forming and our Centrioles are migrating and then I'm like, dude pro metaphase. Sure. We'll call it that Because what even is that? It's just late prophase and This is the part where our Spindle fibers are starting to attach in pro metaphase We're starting to attach. Look at how those spindle fibers are Jockeying around our chromosomes and starting to attach That kind of looks like early metaphase to me. We're jockeying around but it looks like we're lining up on the Equator Now look, I put pro in parentheses because I'm like dude, it's kind of like going away Because it really is sort of like we've jockeied ourselves into Metaphase ah We were lined up All the centrioles are right down centromeres Are right down the middle in the metaphase plate? The centrioles are attached to all those centromeres with the spindle fibers What so cool? Who's next? Anaphase and easy what's gonna happen watch Pull shorten the spindle fibers go centrioles pull it's like tug of war except each chromosome splits How many centromeres do you see though? They get do you see how okay now is this really still anaphase or could we say that we're kind of in telophase right now? Doesn't look like you can get much closer to the pole But look what's happening simultaneous okay telophase is It we concluded that telophase is done. I would argue that that's probably really close to telophase It looks like it's the cell is sort of elongating We should be Sending everything backwards right everything that happened in Pro phase should redo So look look this is a great opportunity To see that okay our nucleolus started to come back our centromere centrioles are starting to disappear but take a look at the chromosomes We have one one in one of each is in each pole and We're reforming the nuclear envelope the nucleolus is getting brighter the nuclear envelope is getting stronger and Cytokinesis is happening while the cytoplasm is actually being divided up and Voila cytokinesis is done We didn't dissolve One thing that didn't happen that I didn't illustrate is the The unwinding of all those chromosomes in the nucleus. I didn't show that But that's definitely happening in telophase so another really good example of the Oh come on now I the drawbacks the There's a word that I'm looking for for images the Downside the I don't know what word I'm looking for that's because it's late. I'm not supposed to do these when it's late Okay, but that's okay Because it's not we're almost done We Have a summary just to look at the what we started with and We went through that that cell is diploid you agree because we've got two copies of every chromosome Went through mitosis and this is what we ended up with like that I actually pulled that from the previous slide and it's exactly the same count the chromosomes Those are exactly the same number of chromosomes. It's identical. So you end up with two identical diploid daughter cells I'm harping on Some facts like right the sisters split the number of chromosomes is the same the daughters are identical These are things. These are qualities that We'll see are different when we go through the process of myosis in the next lecture. I Think that's it. I think that you're about to get at the end slide That was the best part of the whole animation is that I predicted Correctly the end Okay, don't go away. There's one more little blip About mitosis gone bad