foreign hi everybody this is a short video discussing uh more of looking at mitosis and then we'll be looking at ultimately meiosis in this particular slide what I'd like to do is compare mitosis and meiosis in terms of when it's happening in one's life so if you take a look at this of course what has happened to produce these two cells so as I give you an image go ahead and identify is it mitosis or meiosis so for these two uh different kinds of cells this is an egg and these are sperm and of course to produce these people have to go through meiosis then of course the next picture what we're looking at is fertilization and in fertilization we're going to combine the two and become uh that'll become a fertilized egg known as a zygote and then for um this uh organism to appear by a week to look like it at this point eight eight weeks to look like it that would have to be as a result of a lot of mitosis and of course development and then also mitosis to get to month three what about in month five or six what would happen there that's right it would also be mitosis and for now these children these happen to be my own um to get to this point in stage in life they'd have to go through a lot of mitosis and then here also mitosis and then here also mitosis and then here also mitosis now at this point in time in these pictures this is when we don't want to think about it as a parent but they're also starting to go through meiosis okay don't think about that anymore all right good so what we've talked about at this point in time of course in the cell cycle is that there are two main stages um in the cell cycle one of them being interphase which takes up 90 of the cell's life and that's why we saw so many um cells in interphase when we looked at the root tip and of course interface includes g1s and G2 so the other 10 we can see would be mitosis and we saw that in general looking at a root tip that not very many of them were going through each of the stages of prophase metaphase anaphase and telophase so it's only going to be about 10 of the time and then each of those sub phases are going to take some time so and then of course at the end uh in many organisms we're going to have cytokinesis so to kind of put this all together the process of mitosis is of course making daughter cells that are genetically identical to the parent cell so when we say the daughter cells that's kind of a generic term as a result of being split from the daughter cells we're gonna um from the parent cell sorry we're going to see that um ultimately the same term daughter cells is used for meiosis but they're vastly different in terms of makeup so here we have a very simplified diagram which can help kind of get the overall idea of what's going on with mitosis so for example we're always starting off with one cell and ending up with two cells and in the first cell if there's 46 chromosomes the two daughter cells will also have 46 chromosomes if the parent still starts off with 32 chromosomes then each of the daughter cells will also have 32 chromosomes if it starts off with 54 then each daughter's cell will have 54 chromosomes if like there's a particular Fern that has 1260 chromosomes in the parent cell then there will be 1260 chromosomes in the daughter cells so as a general rule we can kind of see oh well if there's two daughters uh two chromosomes in the parent cell that there will be two uh chromosomes in each of the daughter cells so it kind of is a very simple diagram but you'll see later on how it'll help us with contrasting what's going on in meiosis all right so as you know there are four main stages those are prophase metaphase anaphase telophase and then cytokinesis is a separate issue and I've given you a couple of hints about how to remember what's going on so Pro is kind of like pre or beginning meta is like middle Anna is like a part meaning the sister chromatids moving apart and then telophase is the end or two cells okay so um there is a very nice video to watch um that I suggest it's actually more of an animation than a video so let's take a moment and take a look at that okay so the um uh URL was written on the previous page so you could look at that if you want to go over this again this is kind of a fun little program to be able to interact with and get a better sense of what's going on in mitosis so this is by cells alive and what I've done is I've found the mitosis section and this of course is an animal cell we can tell because there's no cell wall and over in this left hand corner we can see um a picture of a real cell and then of course here we have more of an animation on the right hand side we have all the different phases that we're familiar with um and they've also included in between prophase and metaphase Pro metaphase so some people like to include that that detail as well so there's some kind of neat stuff that you can do with this one of them is uh to kind of Move Along slowly and you can see what starts to form so let's take a moment and go back here first of all what are these right here do you remember okay those are centrioles and then these are supposed to be the microtubules that are found in the cytoplasm of course this is the nucleus um with the nucleolus found here and we're in interphase so then when you move forward you can start to see some interesting things happen first of all for the first time you can start to see a little bit of what's going on in here we'll move a little bit further forward you can start to see chromosomes they become a little more distinct now in here you're going to start to see something that's a little bit unusual when we drew these for our assignment one of the things that we noticed was that when I asked you to draw them I would ask you to draw like a chromosome like an X right and then what I did was I had you also draw the centromere okay so here's a centromere now on this particular um program they're using a couple of other symbols here now I used it so the centromere you could count and that could help you identify how many chromosomes you were looking at what they've done in this program and also in our textbook which is why I didn't want you to use your textbook they have included what are called on either side of the centromere these are called kinetochores so let me write that down so these are kinetochores and kinetochores are on either side of the centromere and they're kind of like little handles so they're um if we take a look at it with each um with each um sorry my brain stop for a moment with each centromere there's two kinetochores so let's write that down here for a second so one centromere and for each of those you're going to have two kinetic course okay so what they're doing here is drawing the kinetochores whereas I had you draw the centromere and again the reason why I had to do that is so you could count the number of chromosomes more easily now the other thing that is a little bit funny the way they've drawn these you know that each half of this so let's see if I could kind of indicate what I'm referring to um so on here let me get this to write on here you can see I've got maybe that's not the best let's try it again here right here up to this side and on this side each one of those is a sister chromatid okay so let me line that up here write that down hopefully I'll spell it right sister chromative so there's in this case what I've done is shown you two sister chromatids I'm going to change that to White so you can see it okay so those are two sister chromatids they're showing those sister chromatids separate from each other as though they don't touch which is a little bit confusing because they actually do it can make it you think that they're a homologous pair they're also not using the colors like we did so they're just using four different chromosomes and not indicating if they're maternal or paternal okay so let's take a look at this a little bit further there's some kind of interesting stuff that you can do with this so here we've got the beginnings of prophase you can start to see the chromosomes should become more obvious as they coil and you can start to see the spindle forming the spindle apparatus or the beginning of the spindle fibers and you can see that um the swivel fibers are reaching out ultimately they will grab onto what's showing here a Chromebook kinetic core okay then the chromosomes will be moved to the equator from the spindle fibers and then after metaphase we can see that we get to anaphase where the sister chromatids are being pulled apart they become separate going to either poles I'm clicking it faster because it's taking some time and then at telophase we can start to see that the spindle fibers start to detach and we end up starting getting nuclear envelopes around those chromosomes and they become their own nucleus and then at the end here we're showing cytokinesis again where it looks like at the beginning where you cannot tell what's going on with the chromosomes okay so um this is kind of fun you can try to play with this you can also see it move very smoothly so let's take a look here foreign what's happening in each stage kind of like you're teaching someone else go through the process and then hopefully we'll put it all together for you so hopefully that was helpful for you okay so there is another video here it's kind of a fun one to watch so if you'd like to see that one um take a look at it and hopefully it will help you remember material too this one's a little bit more of a songy kind of thing okay so now what we're going to do is take a look at those pictures that we saw when we were in class looking at mitosis but I would like it if you could um kind of think back and see what it is that we wrote down there's some kind of key ideas that I wrote down too or I I would say to kind of help you remember okay so first of all this one right here what phase do you think it's supposed to be if you said prophase you'd be right and um that's because in prophase the chromosomes coil up you can still see some empty spaces in between the chromosomes where there's just light passing through and of course the main features of what happened in prophase um are that the chromosomes condense and then the nuclear envelope starts to disintegrate and we get the formation of the spindle apparatus um or sometimes they call it the mitotic spindle there's a zillion names for these things but it's basically the spindle fibers begin to form and then the next phase hopefully you can see that um there is very clearly a um a an equator here it might not be exactly straight um but that's definitely an equator where the chromosomes are lining up so that makes this here um metaphase okay so um now what are the dark things here well if you look at it up in here what's being stained by this dark stain are the actual chromosomes so these are you know this the long chromosomes kind of um coming out uh kind of they're the last individuals to get pulled in um to the equator okay so the chromosomes move to the equator and when we see it we also have anaphase in anaphase the chromosomes pull apart you can see their sister chromatids on either half here where you end up getting the dark color in there and of course in anaphase the sister chromatids are being pulled apart by the spindle fibers toward the poles so Anna apart and then finally in telophase which you've got here are the newly forming nuclear envelopes and you can clearly see that cytokinesis has happened so the chromosomes reach the poles the nuclear envelope reforms on each one and then the spindle fibers disintegrate you don't see them anymore and then the cytokinesis can happen now I'm going to show you a really really goofy method that I've shown for students throughout the years and some people really find it helpful so if you wouldn't mind watching the video that I'm gonna make with my hands and it'll be really beneficial if you as a kinesthetic learner do it too okay so let's take a look at this so first of all what I'm going to do is I'm going to take my hands and I'm going to hold them together notice I'm interlacing my fingers the fingers aren't sticking out they're inside and so what we're seeing here is uh not much in between the chromosomes and so what you're seeing here is interphase in an interphase you can't really distinguish chromosomes from chromosomes but in prophase they start to coil and then you can start to see between them so that's what's happening when you see those white spaces in the picture here so you end up seeing in between them leaving the white spaces and then the next phase is going to be metaphase which the chromosomes are lined up along the Equator this way and you can see the ends of the chromosomes or sister chromatids that are sticking out and then the chromosomes get pulled apart and you can see kind of the ends of these right here but when you take a moment and now telophase happens you can't see between them very much and ultimately at the end you'll have two daughter cells with their own nuclear nucleus okay so let's try this again all right everybody if you could do this with me we've got interface can't distinguish between the chromosomes they start to coil and become more obvious you can see in between them you see spaces in between then you have metaphase which the sister chromatids stick out a little bit then you have anaphase in which they're getting pulled apart and then you have telophase where the chromosomes are less distinguishable and they're in their own nuclear envelope and then of course cytokinesis is likely to hurt occur okay so hopefully that helped a little bit let's take a look at some real pictures here because as you know that's a little more challenging than looking at cartoons so a couple of pictures here these are animal cells which look different from plant cells um so first of all just to kind of give some indications here this one is interphase you see how they're oatmealy can't really distinguish between them very well um so that's definitely an interphase right there um down here we've got our anaphase where they're pulled apart and then this one I don't know if you can see the difference but this one looks a little more even colored and then this one looks a lot more um you know obviously separated from each other there's more white spaces in there that's what makes that prophase and then here in metaphase you can see um the spindle fiber alignment not spindle fiber alignment the alignment of the chromosomes just stop there for a second I can see the spindle fibers in there but the chromosomes along the Equator sorry about that brain stopped it happens okay so let's take a look at that one can you identify what's going on there when I take on my glasses which you kind of have to do at this point or get up close you can see it's kind of oatmealy hard to tell what's going on and it may or may not have a nucleolus obvious in this case it doesn't so that's an interphase as well but look at the next one here that's definitely when you can see obvious dark chromosomes with spaces in between so those are the the chromosomes these are where the centrioles are they call this the center zones okay and so that's prophase now taking a look here um you've got this nice straight line in between that is that um theoretical or imaginary line that we call the Equator so this is definitely a metaphase to me often these look like little spider legs on the outside so that's why I refer to it that way in this picture here what is this one same thing right so this is another metaphase this one I can see that they're coming apart and the little ends of them kind of look a little bit draggled so kind of not even that's because they don't have a nuclear envelope around them so that tells me what we've got here is anaphase it is also starting a little bit of cytokinesis that's interesting there too right that's a little early and then in the last one here with these two um you can start to see that they're making you know the nuclear envelope it's a little smoother in this one so these ones are in telophase so let's take a look at these now make sure we're all good with that one let's take a look now at the plants they're a little bit easier to tell um so here you can obviously see a prophase you see how you see those white lines in between that's this going on right you can see in between them um and then over here these are really obvious looking metaphases right because you've got the the spider legs hanging out on either side okay um over here you've got an interface and this interface see that really dark nucleolus that always tells me you know it's probably interface especially since I can't identify what else is going on here then over here on the other hand see how there's dark lines there it's a little bit bedraggled still needs to be a mustache that needs to be cut a little bit but it's all pretty you know dark in between so not like this but like this right and so that tells me it's telophase and then you can see that cell plate is visible so that tells you this uh plant cell is going through cytokinesis that's a cell wall that's going to be finished at the end okay so then let's take a look at this one what is that that's really mushy can you figure out what it is well hopefully you guessed its interface right sometimes you can't tell a lot because there's not much pigment or whatever when you know it was dyed um and it's just not very obvious um let me see here oops let's go back here I want to actually point out this one do you see how it's like this but then it's really starting to get smooth around the edges so that one is a telophase right there and you can also tell because they're kind of small cells right the ones that I'm not divided yet or will divide in the future they're longer and these ones are kind of like small blocks now these two right here um they have a really obvious nucleolus you can see some white space about it but that's probably because the way the staining happened so that is looking at uh interface here okay now the next one you can see a little bit different here there's some white lines in between that's what we're referring to with this right so that would be prophase and then here we've got an obvious looking metaphase with those um the little legs of the spiders coming out that's metaphase right there and here being pulled apart right look very different so that is anaphase and then here do you see how the chromosomes are a lot more dark and like stuck flat to each other and they're starting they will get smoother around the edges right that one is definitely a telophase um I'd have to look closely to see if there's any cell plate looks like a very small one is starting there a lot less obvious than this one so you have to look for all those characteristics to kind of identify where it's going all right so that being said um this one of course we saw as metaphase already um now one thing I wanted to point out here is that uh when we were drawing our pictures in homework 8 you were looking at plant cells which have a membrane around them you don't have cell wall and for that reason you could form that pinching which we called cleavage Furrow okay and so here there's something different happening because you can't have the cell wall pinch in what happens is little vesicles which are like um if you recall vesicles from the beginning of maybe uh it was about chapter four um kind of early on in the semester that their little plasma membranes with things inside of them in this case what it's transporting around is cell walled materials so more likely it's going to be cellulose and it gets dropped off at different locations and then they start to form what we call a cell plate so that becomes the new cell wall all right now next what we'll take a look at are how cells keep track of cell division so for example one of the things that they can form uh that they do form all the time are regions on the ends of the chromosomes on this picture what they've done is given them a fluorescent dye specifically on the telomeres so that little region you can see um is at the end of each of these now these are all um replicated chromosomes so they're little X's but they're kind of flat but so then you can see that there are two sister chromatids here and then on each end you have the telomeres the job of the telomeres is kind of do full do twofold one of them is to protect the chromosomes from being degraded and then also to keep track how many times a cell has divided so um this is kind of a not a great picture but it indicates what's happening if the blue is the regular important functional DNA and then the oranges the telomere every time the cell divides the pieces of nucleotides of the telomeres come off and they get shorter and shorter at some point however you're going to have divisions that result in functional DNA get lost and that's when the cell is going to die so um it's kind of it's life cycle okay and we can also see an interesting relationship between telomere length and the age of the organism that has those so if we take a look at these um on the side here the length of the telomeres in kilo bases so the bases are talking about the nitrogenous bases that are found in the nucleotides so kilobases as thousands of nucleotides here then what we can see is that in the 50th percentile so that means you know kind of average 50 percent of are below and fifty percent of are above um so the 50th percentile of people in terms of their telomere length we can see is a little bit over you know 10 000 kilobases and some people are luckier they have longer um telomeres and some people are less lucky they have shorter telomeres to begin with so um you can see that over time we lose the the length of our telomeres and so some people kind of wonder what if um if age is correlated to telomere length what if we could increase the telomere length is there a way to increase longevity how long we live really interesting questions kind of scary too right so here's an example of somebody who has a disorder in which the person is born with shorter telomeres than the typical person so this is a genetic disorder and this picture is of a person who is approximately 21 22 years old um he was born with progeria and um it's really a tragic disorder because um you know the parents don't have any reason to think that they uh would be carriers of Progeria but you know they um it can happen right two people meet and they both may be carriers for Progeria any case so this baby starts off and very early on you can tell that it's something different's going on um you know by the time uh that these children are six or seven years old you know they're already looking um older and more mature but very short and by the time they're 13 14 years old they might actually start to have um some of the diseases or disorders um that are associated with older age like that of a 60 or 70 year old so they might start having heart problems or arthritis and legs like in the knees or the hips or other joints so and then they also don't live very long so they usually live I think a maximum of 22 23 years old so I think of it as being a very tragic situation um where if you can imagine that in this person's mind they're still you know 17 there's still 11 whatever um but they're they're going to have a shorter life and a lot of it will be you know dealing with disease anyway so an interesting aspect of cell division um I hope that you got a little bit of information to make you feel more confident with the concept of mitosis and um have a good day bye-bye