so let's chat um this is chapter two general biology this chapter is all about reproduction and when we talk about reproduction we're not necessarily only talking about reproduction in a macro sense that's fine that's fine um we're not necessarily talking about reproduction in a macro sense we're also talking about cellular reproduction and how cells get from you know one generation to the next et cetera Etc but before we do that I made two small errors in last week lecture that I want to correct so number one one of them was actually corrected in the lecture itself that was the whole thing about the histone proteins so that the histone proteins have lysine and Arginine which are two amino acids that are positively charged that's what makes them positive right I mistakenly said it was histidine and his lysine and Arginine the second thing is that when I was talking about hydrogen peroxide in terms of peroxisomes right I said that they undergo a sort of bond breaking that looks like this and the reason those arrows only have one end is because those are fish hook arrows those are one electron arrows these are two electron arrows the number of tips is the number of electrons right so that type of bond breaking I called it a homolytic bond Association it's not homolytic it is heterolytic this is called a heterolytic Bond Association hetero meaning two analytic meaning Breaking the Bond breaks into two things right on the one and under two it's called a heterolytic bond dissociation not homolytics homolytic would be like this Bond breaks onto one thing that is homolytic this is heterolytic right okay cool so now that my mistakes from last week are out of the way we can move on to this week and this week we're gonna or not this week it's the same week it's just the next day um we're gonna be talking about reproduction like I said before right and before we talk about reproduction as a whole and reproduction on a species and individual level we have to talk about reproduction in the cell so the first thing we're talking going to talk about is the cell cycle and mitosis right so what is mitosis from your Biology lecture what's mitosis yeah it's just cell division right so autosomal cells are said to be diploid and they contain two copies of each chromosome and then germ cells are haploid and basically mitosis allows us to take a diploid cell and make two diploid cells out of that right so in humans when we have a cell right and it has two n chromosomes meaning diploid right meaning that I if I were to look at chromosome one right chromosome one looks like this well obviously first I have a pair right and that would be diploid right and the chromosome two I'd have a pair in chromosome three I'd have a pair right now it's going to get quite difficult when we start to talk about diploid versus single and double stranded right so normally when we go throughout the you know the life of the cell the chromosomes these are single stranded right and then when DNA synthesis and replication occurs in order to prepare for mitosis these become double-stranded right and it's a 2N for a time they become for it right and we're going to be talking about that in a bit okay so and then why are germ cells haploid right why are they haploid well if we have a if we have let's say some sell only some cell of some organism only has three chromosomes right so they have two copies of chromosome one two copies of chromosome two two cups of chromosome three right so then six chromosomes total well if we have a germ cell so this is a somatic cell and we have a germ cell chromosome one chromosome two chromosome three if we had two copies of each and there's a germ cell it's been combined with another germ cells produce this organism or this self so that'll become the organism right now when they combine there's gonna be 12 chromosomes not six so in order for The Germ cells to combine and create a 2N organism we need n number of chromosomes and what's n n is just however many you have and that means we have three chromosomes so you guys see how this is n and this is 2N so the germ cells are n and the somatic cells are 2N so in humans what does that mean in humans that means that our germ cells have how many chromosomes 23 and the somatic cells have 46. so if I were to take a cell out of my cheek right a cheek cell and I'll put it into a machine and it doesn't karyotype right I would see two copies of each of my 23 chromosomes right and unless they were getting ready for mitosis they'd be single strand right cool if I were to take a sperm cell out of my body and look at that and karyotype that I would see a single strand of each of the 23 chromosomes but not a pain right so that raises some questions number one and and the one that you know is most pressing to the idea of evolution and how people sort of become different is if we carry one copy of each of those 23 chromosomes how do we get any genetic variation we're gonna have to talk about that when we talk about meiosis right and the second thing being how do germ cells perform in the first place like how do we differentiate between mitosis and meiosis What are the signals that occur in order for mitosis slash meiosis to happen right because how does a certain part of the body know to act a certain way and like how do sperm cells know to become haploid whereas everything else in the body knows that they have to become diploid when they reproduce correct so we're going to talk about that but before we talk about that we're going to talk about the cell cycle okay so the cell cycle is basically just a rotation of things that will happen throughout the life of the cell it's split up into G1 s G2 and M and these are phases G1 phase S phase G2 phase right okay so all of these are referred to by a certain term I don't know that term interface interface right g1s and G2 are known as interphase and in my notes Here hahaha it's a very interfaced individual chromosomes will not be visible because they exist in a less denser uh a less dense or condensed form called chromatin right and DNA must be available for replication meaning that in the nucleus kind of unwinds and you get DNA replication or DNA transcription whatever's going on over there right so G1 stage is known as The pre-synthetic Gap right pre-synthetic Gap okay all right so this is where the cell makes organelles and increases in size and there's a restriction point after that I'm going to do that in a different color there's a restriction Point here right what's a restriction point so like if you try to go to a concert right you need a ticket right so this is your restriction point and this restriction point is just known as the g1s Restriction point and basically what's going to happen here is that the cell is going to check to see whether or not it has everything that it needs to move into the S phase correct to move into the S phase and if it doesn't have everything it needs to move on to the S phase it won't right it'll continue in G1 until it's ready to move on to the S phase or until something else happens until a problem is detected in the cell maybe the cell has some aberrant Gene that could cause cancer and it needs to be killed the cell will get killed right but if anything's wrong and the cell determines that it can't move into the S phase it won't does that make sense cool all right S phase is also known as the synthesis phase what do you think happens here we get synthesis of DNA for later mitosis so what do I write synthesis of DNA in preparation for mitosis right so this is the point right here in S phase where we go from this to that single stranded to double strand and that's important because each of those little squiggly lines you see is called a chromatin right it is very specific language each of those is called a chromatid so chromatins right but not just chromatids they're called sister chromatids sister chromatins right because they exist as part of the same chromosome so two sister chromatids make up the chromosome at the S phase of the cell cycle and right in the middle we have this Dot and it's visible when you look at it what is that dot it is the centromere right that dot is the centromere and the centromere is going to be important later right cool that's pretty much all you need to know about yesterday is any questions about that right you guys might be wondering you know how does DNA replication happen blah blah blah how does the sentences occur every now and that we will get into that when we talk into biochem we get very in depth into DNA replication right all right if G1 was the pre-synthetic gap what is G2 post synthetic Gap the post synthetic Gap so this is basically just quality control and right after G2 what do you think we have what is there another one of right after G2 we have another red line another bouncer before the club right we got a restriction point because clearly at some point we wanted to make sure that the synthesis of DNA took place in the proper manner right and if we only check back here we would have no way of making sure that the replication happened properly right okay so like I wrote in my notes right there cells make sure that there are no errors in DNA replication now at and after the G2 phase between the G2 and M if that was the g1s checkpoint what is this G2 m right who's a drake fan I know G4 pilots on a first name basis yeah G1 G2 all right so under g1s and G2 this is when the party can really start happening this is mitosis this is mitosis oh man look at how many people hey hey oh how was orgo good lab or lecture lecture awesome some people I recognize some people I don't welcome welcome I owe you something last time right cash foreign I think you too right no you gotta earn it all right for everyone who's new here hi I'm using facade I'm a second year medical student at city of downstate I'm running this lecture for the MCAT um also before you guys came in I had a little QR code up on my laptop to sign up for an email list associated with this program um this man right here he has a photo of it but if you guys are gonna stay the whole time I will have a like a PDF of it up on my laptop also very informal lecture if you guys need to leave early and you like don't want to bother the guy while I was taking notes come up to me I'll show you the QR code you can scan it you can feel free all right we were just having a little talk about mitosis and you came in at just the right time because the party's just about to begin all right cool so um actually you know what my laptop might die while we're here so I am going to instruct one more person you yeah you were here the whole time last time bring your phone yeah bring your phone take a photo of that all right cool your name again and yours Sarah my sister yes that's why I remember so um we talked about G1 sg2 Okay blah blah whatever all those collectors together are collectively called interface right now the reason it's called interphase is because mitosis is broken up into phases as well so it makes sense for scientists to be like everything that happens before mitosis is a certain type of phase and everything that happens during mitosis and after mitosis also known as a phase right so we go interphase mitosis interphase mitosis interphase mitosis interface mitosis until we die right and that's basically just what happens to cells correct unless you're a germ cell in which case you undergo meiosis and let me talk about before you become haploid is that a big one correct all right cool so are we ready to talk about mitosis or do you guys want to copy this down like a little more if you guys like to take a photo please go ahead feel free because we're going to keep moving the first step of lectures will go slow like they'll take a bit more time if you guys weren't here last week it took us two hours and 15 minutes to get through the first chapter of biology um which is normally how long it takes but as we go on the lectures will take less and less time especially when like we get to the lectures that I genuinely enjoy because I don't really like I don't really enjoy this stuff all too much I just know it uh but we when we get to like Cardiology we get the homeostasis we get Endocrinology we'll do a bit of technology today when we talk about the menstrual cycle um but it's fun it's a good time everyone ready let's get keep moving that was exciting like 10 people poured into the room all right so who thinks they know about mitosis it's not trick question you can raise your hands who's like learned about mitosis before yeah if you think you know about mitosis you do because it's almost as straightforward as everyone has always taught it to you and the MCAT doesn't really discriminate either too much anyways so when we talk about mitosis what we're going to do I'm going to write it up here right and it's split up into phases so here I'm going to draw a line and we're gonna do I always forget them prophase your new metaphase anaphase and telophase or telephones whatever you want to say okay so uh before they talk about mitosis they talk a little bit about control of the cell cycle like we said before we have two restriction points what were they again it was the g1s and then the g2m correct so that's where the cell kind of checks to make sure that things are going properly right so right here in my notes I have in the g1s phase right this cell determines the DNA is good enough for synthesis right there's no problems in the DNA because there are problems in the DNA what happens usually cancer right and G2 or you're just going to sell them to work right and in g2m a tensor adequate size and existence of organelles for splitting right because when if you give a daughter cell everything that it needs we don't give it a damn mitochondria it's gonna die right okay cool what do we say was important about mitochondria last time what was so special about mitochondria huh well yes but unique about mitochondria other than that they had their own DNA and what else you get it from your mother every single mitochondria in this room can be traced back to the first female human being to ever exist right it's quite cool and the MCAT really wants you to know that fact if they ever talk about mitochondrial DNA and any sort of diseases that happen because of mitochondrial DNA you got that disease in your mouth there's no other way it could happen why because sperm don't have mitochondria sperm cells are not built with mitochondria seminal fluid has fructose in it which the sperm use in order to do the rest of glycolysis to power their motility but they do not produce mitochondria and they don't have mitochondria and they can't do electron transport and the citric acid cycle blah blah it just wouldn't be beneficial right all right now here's the thing the MCAT the books at least right like these are the books I'm using are I humbly request that you get them the Kaplan MCAT books they're quite good you can get them used you can get them new it doesn't really make a difference yes does not matter what year as long as you don't go back to like 2008 I think you're good uh mine are 20 21 22 because I was fortunate enough to be able to afford the ones that were for the year that I was taking them but I know that's not you know everyone's desire or what everyone can do so if you guys want to get them from someone who took the MCAT three years ago Mike I did right because my books are now two or three years old uh feel free and it'll probably be the exact same information and if it's not the exact same information it'll still be on this board right all right cool so the book makes a really really small reference to cyclins and cycle independent kinases basically um Cyclones and cycling dependent kinase you don't necessarily have to know for the MCAT but they are these molecules that kind of come and go throughout the cell cycle in order to kind of signal to the cell that this is where we're at and this is what we need to do next do you even know about them not really right but what's well first of all before before we do anything else there very specific thing what's a kinase because I don't know what a kinase is we're going to talk about this over and over and over again the kinase is an enzyme that phosphorylates something using ATP it uses ATP to phosphorylate something and the reason that's an important distinction to me is because there are other enzymes that don't use ATP to phosphorylate things they use phosphate groups inorganic phosphates right so if this enzyme is using ATP in order to phosphorylate it is known as a kinase right so here we're talking about cyclins and cycle independent kinases a cycle independent kinase is a kinase or an enzyme that phosphorylates something using ATP that is dependent on a cyclin and a cyclone is a type of protein so cyclins rise and fall throughout the cell cycle hello Sasha rise and fall throughout the cell cycle right and as they rise and fall they activate and deactivate certain cycle independent kinases that will go and phosphorylate other proteins and things throughout the cell in order to kick off different parts of the cell cycle that's all you would need to know if you get a passage about them and it explains a little more more power to you but I don't know much else about them anyways all right and I have no problem admitting that all right then we make like a little little sort of segue into cancer right because cycling cycle independent kinases are usually like how people talk start talking about cancer and how people begin to sort of you know um begin their discussion about cancer so when we talk about regulation we talk about checking stuff like that what's the biggest check when it comes to cancer everyone knows the buzzword it's a gene p53 right well also this isn't under like the mitosis metaphase I'm just using it because I put this up too early but p53 p53 is a gene that goes through a protein that checks the rest of your DNA and checks to make sure it's okay all right also you guys are right in front of the camera right if that camera ever stops recording you tell me okay cool you're in charge because I don't have eyes that like stretch over there okay so p53 is a gene that goes for a protein that is able to check to see whether or not the DNA is okay if p53 is mutated you are simply you are you are simply out of luck right not always right the cell can still recognize that there's a p53 mutation and then destroy that cell right and what is it called when we get controlled and organized cell death apoptosis what is the other type of cell death necrosis right necrosis when you get to medical school you're going to learn that there's like 70 different kinds of necrosis it's like coagulated necrosis and liquefactive necrosis and fat necro and it's all in your pathology lecture and it's just the worst thing ever you have to like look at a picture of like it's like a photo on a screen right and it's just purple and they're like what type of necrosis I don't know dude purple right it's stupid where's my Red Bull okay so now that we've talked about cbks blah blah let's finally talk about mitosis right prophet get condensation chromatids number one number two right you get a disappearing of the nuclear membrane nuclear membrane kind of dissolves right a lot of DNA was held inside a nucleus right and now it needs to be able to move around the cell because what you're going to do is you're going to rip these DNA pairs apart you're going to pull them away from one another right so you're gonna pull them to opposite parts of the cell and they're contained within that membrane they can't do that so you got to pull the DNA part and then assemble them into a new membrane that exists in the daughter cells right so that's what we're going to do one more thing they say is that centriole hairs separate uh I for one and let me give you guys a little bit of background okay so I studied for the MCAT for six months and in those six months I started for 500 Plus hours right 500 550 something hours like that right I took six practice exams Each of which I think were like I think the correct number is like 230. well let's say 200 questions right that's 1200 questions right there and then I did all of you world which is 2500 questions so what's that 2500 1200 is 3700 and I did all the AMC material let's say that bumped me up to 5 000 questions and then I tutored six different people on the entire MCAT curriculum let's say I did 5 500 questions in 5 500 questions I've been asked about centriole pairs once it's not going on the board okay it's not going on board what's going on the board is the stuff that I've been asked 10 20 30 times about all right make sense cool so when people are like oh dude but like I read this thing in the textbook and it seemed really important but you didn't talk about it I didn't talk about it because it's not important okay you're talking to the guy who's done like 6 000 MCAT questions and then how many have people done when they come to me and I'm not putting them down or anything zero right so I've done six thousand they've done zero and they're like oh we're gonna seems so important it's not and trust me and I don't mean me to say that put you down I mean to say that to put your heart at ease that not every single thing in this book is important and like I said before you maybe need to know 60 to 70 of the information well you don't even need to master it you need to know 60 or 70 of the information well to do really damn good on this test all right cool so like I said Central pairs are not going on the board all right what benefits right everyone knows metaphase what does meta mean remind for my language people Meta Meta means the middle right so chromosomes meat in the middle of the cell what's the middle of the cell called when it's metaphase what do you get your dinner off of a plate the metaphase plate the metaphase plate right okay cool so you remember those centrioles that I talked about before they're not going on the board but because you never really asked about them but what we are going to put on the board is the fact that in metaphase what happens is that those little centrioles those things that exists they move to the opposite end of the cell so now they're important so the metaphase plate exists that's where all the chromosomes are and this is when you can start worrying about the centrioles because here is just like all the centriolet pairs form and then they split out and then they start forming they're spinning it no this is where we start worrying about them centrioles at opposite ends of cell use what do they use these spindle fibers to attach to attached to what attached to what is it called yeah the centromere attached to centromeres right the little things in the middle that we talked about the sentiments right cool why are they attaching that there right these are anaphase what's going to happen and anaphase they get pulled apart what gets pulled apart this is really damn important what gets pulled apart in mitosis because the things that get pulled apart in mitosis are not the same things they could pull to part of meiosis the sister chromatids get pulled apart pulled apart where to the opposite ends of the cell one goes this way and one goes that way and here are the cell borders form and these condense right and these meet in the middle those Pillow fibers go gotcha and just pull right opposite ends itself what happens is in two locates what happens some people call telophase cytokinesis right those are two different things cytokinesis is a part of telophase number one is cytokinesis cytokinesis what is it split the cell in half right right what else you get a new nuclear membrane brand new right off a lot chromosomes and coil right and the spindle apparatus dissociates and that's it through my notes right so as a little as a little uh what's it called exercise at opposite ends of cell yeah so Central and the cell use spindle fibers to attach to centimeters right so as a little exercise or you know a recognition test visual recognition right I'm going to draw a cell right here and this is the cell of an organism that only has one chromosome right and prophase right single or double stranded in prophase single or double Right double right and then those little centrioles appear but they don't matter until we get to metaphase right prophase metaphase and this diagram is not original from me it is it is quite literally just in the MCAT book anaphase until effects oops you guys see that I know it's quite small I apologize for that and I hope you guys can kind of see what we're doing okay so that's mitosis all right what are we going to talk about after mitosis meiosis right makes the most sense doesn't it everything makes sense that's the thing if anything ever doesn't make sense you're the one in the wrong that's what science will teach you if something doesn't make sense you probably don't know enough and I've been taught that many times by being in medical school okay do you guys have all this down or do you want a minute you guys want a minute please feel free to tell me good all right so meiosis is a lot like mitosis in some ways just slightly different it's like meiosis went to college and got a degree and knows how to do more stuff right and it's special but as you guys can imagine when you take on a lot of responsibility and you begin to do more things with your life there's also more of an opportunity for things to go wrong right like the other day I wasn't feeling so great I had a sinus infection that I'm finally better from right and like I forgot my charger at home and then I forgot my charger here and I lost my laptop charger blah blah whatever and then my necklace broke and I missed the bus and then I forgot my wallet at home and like everything was just going wrong and it was just because like I was sick and I was trying to go home at the end of the weekend and then my car broke down the last week and ball and there's a lot of things going on so a lot of things could have went wrong right in meiosis there's a little more going on than mitosis so the MCAT also likes to focus on what could go wrong right so try to keep in mind when we talk about meiosis you know what could go wrong and what would happen if something did go wrong because interestingly enough things do go wrong and when things do go wrong you were born with horrible congenital defects what does congenital mean you're born with congenital right congenital congenital A congenital disease is something that you're born with right so we're talking about meiosis well bastard been talking about this guy's night brain how many years has it been two men ten all right meiosis is split into two categories and scientists are so creative first one is called meiosis one and the second one is called meiosis B no I'm kidding meiosis two right all right so over here so inside instead of the big line like the big four lines we're gonna go like this and on this side we're gonna have meiosis one and here we're gonna have meiosis too why isn't it spelled like this because mayo means muscle that's why it's not spelled like that all right hey very close attention to what goes on the board now this is separation of blank and this is separation of blank who can fill in the blanks my man can you catch foreign louder homologous chromosomes all right sister chromatids one of these terms we saw before this is the chromatids thing right and one of these terms we haven't seen before what are homologous chromosomes they're chromosomes of the same type right so in my body in my cells I have a chromosome one from my dad and I have a chromosome one for my mom and they float together right next to one another or wherever the hell right and they are homologous right homologous chromosome both copies of chromosome one right and even though in my body right because I'm a genetic male correct in my body I have an X chromosome and a y chromosome those are still homologous because they are of the same hair right I have 23 pairs of chromosomes 22 somatic and one sex chromosome pair correct in women they're the same and in men they're different right Okay so separation of Molly's chromosome happens in meiosis one and separation of sister chromatids happens in meiosis II there are a lot of new faces if you guys missed the last lecture it is recorded and it's up on my YouTube channel um there's a little QR code going around a couple people took a photo of it if you need to leave early get it from one of them I believe it was you and it was you right so but if you're saying the whole time I'm gonna pull it up on my laptop later or we'll discuss after that right okay so meiosis is clearly different than mitosis right so meiosis II is basically just mitosis right but meiosis one is a little different correct okay so the same things need to happen in order for something to go into meiosis we got to get the replication the DNA synthesis the organelles and everything right but before that we need to separate homologous chromosomes before anything else and meiosis one is still split up into phases like mitosis right so we have prophase what comes after prophase metaphase what comes up in metaphase anaphase what comes after anaphase telophase right all right teal things cool so this is basically the same thing like I keep saying it's the same thing with slight differences okay prophase one prophase oh also I forgot to say each of those gets a little number next to it now that we're special and it's just a one because prophase one metaphase one anaphase one two of phase one right so prophase like before the chromatin condenses homologous chromosomes you know they they form the little blah blah whatever pairs right they form this thing called a tetrad right so they they kind of line up and they line up next to another natural tetrad right okay now one special thing happens in prophase so this is basically same as mitosis except that tetrat formation where they stand next to one another side by side a very special thing happens what's that very special thing that happens crossing over why this crossing over exist let's talk for a second so I am a combination of my mom and my dad correct hopefully no one asks Okay so this is the chromosome that my mom gave me and this is the chromosome that my dad gave me right and let's go back into my Mom and Dad's Body when they were getting ready for my meiosis mitosis whatever right now my mom got a chromosome from her mom and heard that right so this is the chromosome that my mom's mom gave her and my mom's dad and whatever right and then there right so now we're talking about my parents that's my mom's mom my mom's dad my dad's mom and my dad's dad right okay now if crossing over didn't occur right and we just had oh I need to double strand these oops we're gonna look at those for now because I don't really need two two of them so when they line up in the tetrad like this they get super close together right and what happens is that these homologous chromosomes let's say this isn't my dad this chromosome one right and both of those are the same copy of the one chromosome he got from his mom and those are both the same copy of the chromosome that he got from his dad correct what happens is that little sections of the chromosomes they swap with one another right they swap with one another so what happens is that a little bit of the green goes on to the rest of the red and then the red and the rest of the green right and then the same thing happens over here with a little bit of the red went on to the rest of the green and the rest of the red went on to the rest of the green and now you can see that these chromosomes when they eventually part ways they are solid mixes in some way or another of the chromosome that his mom gave him and the chromosome that his dad gave him does that make sense do you guys understand that all right so that's the importance of crossing over it implies a level of genetic variability right because if you go back and you look at the right chromosome and you trace it back from my dad's mom that chromosome must have been a mix of her dad and her mom and you can trace that back to her dad it would be his dad and his and we get these crossing over events that happen at each and every single generation of donation of genetic material that instills a level of diversity that wasn't seen before and that's why I don't look exactly like my mom or I don't look exactly like my dad although my dad would differ right he would say that I do right but that's necessarily what happens when crossing over occurs right so do you guys understand that you guys understand how this increases your genetic diversity that's a very important part of the first step of meiosis one understand all right cool what's next metaphase basically the same those homologous chromosomal pairs line up in the middle metaphase plate same thing right animates what's different about NFLs those homologous chromosomes are going to get pulled aside instead of the sister chromatids so that little thing pulled two opposite sides of the cell right homologous chromosomes pull through the opposite side of the cell correct okay all good cool teal face is basically the same except the chromosomes are really unwind after that because the job's not done right so at the end of meiosis one you basically have two cells well at the beginning right we had this and now you have this whereas if this were mitosis you would start with this and end up with this do you see how that's different because these cells are 2N 2N single stranded this is 2N double-stranded But Here We Go From 2N double stranded to n double-stranded so these are haploid cells these are already haploid cells does that make sense ploidy is really difficult to understand it can get tough employee is quite difficult so that's why I keep trying to map out exactly what's going on in mitosis meiosis right that understood I know my writing's quite small I'm trying to write larger I'm just not used to it yet I've actually never lectured a class like never doing so so all right so we've talked a little bit about meiosis one and now obviously meiosis too so prophase two anything special about prophase two well same thing if you're grounded that's disappeared Central May blah blah right so nothing special metaphase two nothing special anaphase two so what happens at anaphase 2 the homologous chromosomes pulled up are here and now the sister chromatids are pulled apart here right that he's known as black separation of all whatever also a disjunction right deal phase two nothing special so nothing special nothing special sister crumpets fall apart nothing special right this is basically mitosis right is mitosis but you already have like that little double thing right there so see we take this and funnel into meiosis too and that becomes this so we went from this 2N double-stranded to end double-stranded and then we get two n single stranded and that is our germ cell and for women it's eggs or OVA ovum singular and for men it's sperm sperm singular right damn oh yeah so you have the center beer right there we had the little centrioles and what's gonna happen so that's metaphase basically and what's going to happen is that those centrioles are going to pull the sister chromatids apart in the opposite ends of the cell and you're going to get like that line down the middle that they're going to split off eventually and that's how they're going to separate it does that make sense oh that one is going to look like that's another good question because that double is going to get pulled by the century the centriole right and then this double you get pulled by the centriole right here I said a term earlier called non-disjunction right so right here this is called disjunction where the sister the homologous chromosomes they're pulled apart right disjunction later we're going to talk about a problem remember I said there's a lot more going on so there's more of a chance that there's a problem right we're talking about something called a non-disjunction error right where anaphase one fails to pull apart a homologous pair of chromosomes and what happens is that instead of getting this you somehow still end up with this and an empty cell a cell that has two of the copies and a cell that gets none and in humans sometimes that's not a problem well it's always a problem but it's not a problem for the formation of the cell but if that cell gets fertilized down the line now you've got a problem who knows when the diseases that can happen due to a non-disjunction error Turner syndrome is one of them that could happen yes can you catch can you catch nice Down syndrome is another one I think try something 21 is Down syndrome so there's Turners there's kleinfelters there's Down syndrome and there's xyy or Superman syndrome right all right cool all good here let's move on so why is xyy syndrome called Superman syndrome well it's because you have two Y chromosomes does it actually give you superpowers no I think it makes you infertile sorry yeah aggressive and infertile great combination no it can happen yeah um I mean considering the Y chromosome quotes for like testosterone production it can increase your testosterone but then again like normal testosterone males varies over very very large margin so like the lower bound of normal testosterone is like 200 something and the upper bound is like 970 nanograms per deciliter so it's possible that like people have overproduction it just doesn't push them above normal down um that being that right see you guys next time thanks for stopping by all right now we've talked about meiosis and the formation of germ cells we're going to talk about the reproductive system um so they talked about X and Y chromosomes right so XY is male XX is female right and that's determined by the 23rd pair of chromosomes so yep one through 22 and then you have your sex chromosomes and your stats chromosomes can e to the XX or X Y right you always get a y chromosome from your Gap if you have a y chromosome you got it from your death X chromosome can become your mom or your dad right why am I bringing that up it's important because when we start talking about x-linked diseases you'll be able to track them so before we do that now that we're talking about chromosomes and everything before we talk about the reproductive system let's talk a little bit about x-link inheritance right let's talk a little bit about that so I myself this is a true story I am colorblind I am red green colorblind right and colorblindness is a trait that exists on the X chromosome right so if you were to karyotype me and write out my genome you would see a defect and my X chromosome that confers colorblindness who did I get that from Mom I had to why did I have to get it from my mom because my dad gave me that and my dad didn't give you that I'd be a woman right and my dad gave me an extra I'd be a woman I'd be one of my sisters right now let's take a look at my sister's who can figure out given the information I just told you that my mom gave me color blindness are my does let's talk about my sister Sarah right I got two older sisters not you does Sarah does her karyotype look like this or does it look like this or does it look like this can you figure it out give me the information I gave you no you need more information what are the two questions you need to ask is my mom colorblind is my dad colorblind and is my mom a carrier are the questions you need to ask right because just because my dad gave me the Y chromosome doesn't mean he's not colorblind what if he's just like me and he got that from his mom right so you wouldn't know so you don't know the genotype of my sister right okay let's talk about how I got that so this is my mom right and I'll tell you that my mom got that from her dad because her dad is colorblind right and my mom's mom is not colorblind nor a carrier so my mom is that so like she got that from her dad and that from her mom and my dad he's not colorblind he's not right so we got the Y chromosome from his dad he had the extra chromosome from his mom right do we know if his mom's a carrier or Not by that no because if she was there'd still be a 50 50 shot of her passing on that defective or good X chromosome right so those are my parents who remembers Punnett squares that's my mom and that's my dad and there's me so when you see a male with an excellent disease like color blindness or hemophilia I think hemophilia is excellent right when you see a male with an excellent disease right it had to have come from Mom and when you see a female with an excellent disease that means something special when you see a female with an x-linked disease right especially an excellent recessive disease because hard blindness is what it's x-linked recessive meaning that you need two copies or if you're a woman you need two copies and if you're a man you need just one copy because you only have one chromosome right but since it's recessive in women it needs to display like this so if a female is colorblind you know one thing off the ring her dad's color blind has to be because the dad has to pass on the X chromosome so her dad is definitely like this and where did that one come from comes from the Mom but Mom could be this or this here it's a 50 50 shot she passed that on and here it's definitive does that make sense do you guys understand x-linked inheritance okay cool the book does a lot of talking about the reproductive system I think it is best done through diagrams so if you guys would like I do urge you once again I'm saying to get these books right the Kaplan MCAT books look through the diagrams all that stuff you have it good all right look through the diagrams and everything like that that's where I get all my notes um and that's how I sort of you know um learn all this stuff I will do very very crude drawings of things that are in the book but you should definitely take a look at them one more thing the Y chromosome it's special it contains a specific Gene that the X chromosome doesn't have what is that Gene called it's called the sryg it is called The Sex determining region why sex determining a region of the Y chromosome right and this activates at I believe six to eight weeks of gestation I'm in unit five of medical school right now unit four before summer break was reproduction I hate this term now because I had to learn every single thing that happened inside of a fetus when disactivated it was the worst all right but all you need to know is that this codes for male gonad formation so basically your balls drop for the first time right that's basically what happens because before that the fetus embryologically it looks like a female it has ovaries or like what will be comma ovaries and whatever whatever and if this Gene never activated right or if the transcription factor is that code for this activation or the different proteins and stuff like that that code for male gonad formation if those never occurred it will continue to be a female so by this Gene we confer male sex the sry six eight weeks of gestation so that's what it activates what's Jeff Station it's like when the baby is developed inside of the model right all right cool let's move on male reproductive Anatomy and physiology so first we have the testes or the testicles which are the functional unit of male reproductive Anatomy that's where testosterone produced most of it that's where furnace produced et cetera et cetera why did I say most of testosterone producer one other place in the body that happens you don't need to know it but fun fact it happens in one of the place of the body I'll let you guys look that one up for later oh no it's not a question but I'm just saying that testosterone can be produced in one other place in the body you don't need to know it I'll have you guys look it up for later good guess though all right in the testes we have these things called seminiferous tubules seminiferous tubules these produce sperm this little arrow down from an underlined object means that this is a part of that or I'm elaborating on something right so the seminiferous tubules are a part of the test Suites the testes also have interstitial cells of lady probably the dude who found them right and these produce testosterone which is eventually going to make my hair fall out special question what does testosterone turn into that makes men's hair fall out sorry well if estrogen made your hair fall out you wouldn't have it it's called DHT that hydrotestosterone and some men in later life go on a medication commonly known as minoxidil right and minoxidil inhibits the conversion of testosterone into DHT to minimize hair loss cool interstitial cells of leading l-e-y-d-i-g Laban interstitial cells of later they produce testosterone and the seminiferous tubules produce sperm right from the seminiferous tubules the sperm enter the epididymis the epididymis right and this is where sperm are stored until ejaculation I always hate teaching this chapter because what happens is I begin teaching a student the empath for like the first time right and we talk about the cells we don't like mitosis and meiosis and literally the next time I meet with them I start teaching about and balls it's just the worst it's like not a good look but this is the way the textbook runs so I'm gonna have to teach it so please bear with me I promise it's not all like this so the epididymis right it what do you guys are medical school and you do anatomy lab and you get to hold the testes right you like hold them dissect them cut them open look into them you have the dimness and kind of sits on top of the testicle and it's connected by a two to the rest of the reproductive system because the testicles they hang and then the rest of the system is inside the body why do the testicles hang the ovaries don't why do they hang good job can you catch the bodily temperature is too high for sperm to survive right if the testicles are inside of the human body they would die and men would be infertile right and then no more human race bye bye right which is why there are muscles that are not under our control like men's control that drop and Elevate the scrotum which the testicles fit inside of depending on the temperature when the body is very hot like when you're sick the storm drops and the testicles move away from the body and when the body's cold or It's Cold Outside they move closer to the body right in order to control and thermoregulate the ideal temperature for sperm formation it's a really beautiful process it's very interesting right cool so we talk about ejaculation right so in ejaculation sperm travel to the vast deferens but that's definitely which is the tube that the epididymis connects up to right and then from the vas deferens they go into the ejaculatory duct and this is bilateral right so the left and right testicle go up the left and right that's the difference into the left or right ejaculatory duct and then those two ducts use right those two ducks fuse into the urethra into the urethra which is actually like a lot of people think that urethra is just like the piss hole right it starts inside the body so urethra continues out towards the penis right so it's it's literally the hole that goes through that's the urethra but it starts inside the body and then the urethraid goes into the penis and the sperm will exit with the seminal fluid and blah blah whatever it is right one thing they didn't mention here because nothing really travels through it it just like inserts things into Calpers lab right the caliper is flat or the Volvo urethral gland is going to add some of the seminal fluid which we're talking about in a second so right here in my notes sperm prizing through the reproduction system makes with seminal fluid produced by seminal vesicles the prostate and the prostate and the bubble urethral gland or the Calpers gland right and produces clear viscous fluid that clears out your ether ballline okay that's important so the one thing about the Calpers gland which is one of the three things which produces seminal fluid but you don't really need to like keep that in mind the one thing you do need to know about the Calpers gland also known as the ball bow urethral gland the calipers gland right it produces fluid that quote-unquote cleans out the urethra before ejaculation sorry yes precon that's what this is beans out the urethra prior to ejaculation okay so besides that why why why does that need to happen why do we need to clean out the urethra before ejaculation yeah and acidity acidity did he catch oops I got it yeah so urine is acidic for what reason well urea right urea is slightly acidic and if sperm mixes with that acidic environment is possible that some of the sperm die right they die and that means lower chance of fertilization right so we send out fluid in order to a lubricate the urethra and B make sure that the sperm don't die right okay the book goes on and on about spermatogenesis like over and over again I have two lines of notes about it I've also maybe seen two or three questions about it ever I'm not going over it would you like to study it yourself you're more than three are we all good on male reproductive Anatomy okay so just as a diagram of like how all this works it's like one-sided this is the testicle this is the epididymis this is the tube leading up to the vas deferens right and then it connects through all the garbage over here and then after you're eating right like that's the calipers and the prostate and blah and everything and the ejaculatory abducted all of that right and this is like the best drawing I could possibly do I promise you I'm a much better speaker than I am an artist I hope you agree good all right it's going also if you're wondering why I'm not using the entire board because of that thing let's talk about female reproductive Anatomy and physiology by the way I use shorthand for male and female as well you guys have probably seen them before this is mail and this is female it usually goes up yes it usually goes like this as to not confuse one with the other yeah I believe it's up and to the right okay that's funny all right cool um this is for some reason entire textbook a lot more simplified than male anatomy although it is probably 10 times more complicated in real life um but the only thing they want you to know about is the ovaries which consists of thousands of follicles right we have the ovaries and one of those follicles each month will develop into a into a Excel it's very cool when you guys get to medical school and you look at histology of the ovary so basically you take a slicer and you look it under a microscope you can see like seven eight nine ten follicles at different stages of development right and then what happens is that when one of them becomes the mature egg it releases chemicals that make all of the other ones stop developing it's very cool it's very very good and then they restart right we will be going pretty in depth about the menstrual cycle and it's ridiculously complicated I just need you to stick around with me I don't know why they put it right at the beginning of the book because there's a whole chapter on endocrinology and it would have been way better to put it then but they put it here instead but I guess it's a good introduction to how hormones work okay all right you have the ovaries right and then that's kind of it we also talk about the fallopian tube and the uterus right so the fallopian tube the egg cell travels to the uterus via this canal and what's special about the fallopian tube this is this is normally the site of fertilization can you catch cool right and what about the uterus that's like the big balloon that's like HQ right it is a muscly organ that connects into the vaginal canal right so if we had the uterus over here very very muscly surrounded by smooth muscle like this right it would thin out over here and this entrance here would be what a very very small pinhole the cervix and this would be the vagina and the vaginal canal because the vagina is the outside and this is the vaginal canal and this is the uterus it has a little bulb top right here it's also incredibly small like when I did dissections an anatomy lab the uterus is maybe that big which is wild when you think about how large it gets when a woman gets pregnant it's ridiculous it's not even the size of my fist and then on either side it connects via Fallopian tubes into the ovaries ovaries fallopian tube uterus cervix vaginal Canal vagina that's what you need to know in terms of female reproductive Anatomy and this all floats right here just at almost at the level of the belly button is the top of the uterus and then it goes down right the ovaries hang out right over there okay cool this one yeah so the uterus is a muscly organ that connects into the vaginal canal right the fallopian tubes they are lined with something they are completely filled with something what are they filled with little hair-like structures it was very specific things Celia so what happens is that when the egg cell exits it floats into the fallopian tube and it's gestured along it's just it's slightly rocked towards the uterus and it's just gently glided along the way by the Cilia right where else in our body do we see cilia you said last week where the respiratory tract right and that's how we don't just like gently Glide things along we kick pathogens out of our respiratory track and cough them back out right cilia what are cilia made of you said last week well what like what structure what structure makes them sillia someone look it up and tell me what are cilia made of you had a question what are cilia made of microtubules microtubules make up cilia right so in medical school you will learn about a specific disease that confers a problem with four main microtubules and these people are a infernal whether you're a man or a woman why because you need flagella for sperm and you need cilia for women and they get repeat upper respiratory infections because the Cilia in their respiratory tract it doesn't work it doesn't get the viruses and pathogens out so it makes sense that is what we call pathophysiology so that's called Cartagena syndrome right protagoner syndrome I mean Cartagena syndrome you can have the destruction of cilia and that will necessarily might not allow you to have the sorry includes microtubules and you won't have the function of cilia the ball okay cool cool uh they go on and on about oogenesis which is the formation of sperm um all right and now unfortunately I have to torture you before I torture you and we start talking about the hormones I'm going to stop the recording and we're just gonna have a chat that's like not important to the video