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Current time:0:00Total duration:9:35

Zygote differentiating into somatic and germ cells

Video transcript

in the last video we saw an egg from our mothers fused with a sperm from our fathers to form a zygote that would keep replicating and turn into us if this is this lets let's say this was the sperm from my father that fuses with the egg from my mother and then this is I goat will keep replicating and eventually turn into Sal and make a video about fertilization so how does that actually happen so now that this zygote has the diploid number of chromosomes and once again they're referring to that as 2n where n would be the haploid number 2 n would be the diploid number and in the case of human beings n is 23 so in the case of human beings n is 23 and 2 times n of course would be 46 chromosomes have my full contingency of chromosomes here I got a why sex chromosome from my father X of course from my mother so I'm going to be a male and so what then happens well now through mitosis this zygote is going to keep replicating so it will you know after 1 so after 1 and we're going to go into the details of the mechanics of mitosis but after one round of mitosis it is now 2 cells it is now 2 cells and I'm going to draw it once again I'm not going to draw it at scale it's now 2 cells I want to make sure I have enough space on my little chalkboard here and it has 2 cells instead of drawing all of the chromosomes let me just say that each of these chrome eat in my nucleus I still have 2 n I have the diploid number so I each of these 2 cells that it is differentiated to still have the full contingency that's what mitosis does it essentially replicates the entire cells you have the same number of chromosomes and then this process is just going to keep happening these two characters are going to replicate are going to replicate and so then you're going to have through mitosis and now you're going so this is another round of mitosis right over here mitosis so they just keep duplicating themselves and each of these cells have the full have the full contingency to end the diploid number of chromosomes for well in this case is going to be 46 for human being and then this process is just going to keep happening so this process is going to keep happening I'll do dot dot dot to show that you know a lot of this has been going on so mitosis is just going to keep happening and so eventually you're going to have thousands of these cells and eventually as we'll see you're going to have millions and ten millions of them so let me draw them really really really small so there's a bunch of them there and and each of them each of them are going to have the diploid number of chromosomes they're going to have 46 chromosomes 23 pair of homologous chromosomes so we now have a big ball of these here and these cells some of them are going to they're going to differentiate into me they're going to differentiate into the different parts of my body so for example these cells right over here might eventually they'll keep replicating and but then it's them and their offspring might eventually differentiate into my brain cells these cells here will keep replicating and they and them and their offspring I guess you could say the things that they replicate into might differentiate into my heart these right over here might differentiate into into my lungs and of course you know all of these eventually will differentiate into all of the different all of the or and they and their offspring will differentiate into all of the things that make me me and so you go you have a lot more of this mitosis you're eventually going to have you're eventually going to have a human being so let me just say this is more mitosis going on my ptosis and now let me have make an attempt to draw to draw a human being so that doesn't really look like me but well I have a lot of hair so that's my big eyebrows as well well it still doesn't look like me but anyway you get the point and so and I'll try to draw him fairly or fairly quickly but this is obviously not my best rendering of a human being but you get the general idea nice broad shoulders that's nice alright so let me let me I'm focusing too much on drawing this human being but anyway I give you get you get the general idea I don't my stomach isn't that quite that flat but anyway you get the general idea so this it'll eventually differentiate into a human being these cells here and pink eventually differentiate into the cells in the in the brain these cells here eventually differentiate into the cells into the lungs and obviously have this at this scale the cells are way too small to even see these cells differentiated into the cells of the heart now I want to draw an important distinction here because most of the cells that I've just depicted here that are just a product of mitosis these are your I guess you could say these are your body cells or these are your somatic cells so these all of these cells that I'm pointing out in your heart your lung or brain these are somatic cells or body cells somatic cells and so you're probably wondering well how do I eventually get these haploid number cells how do I eventually get if I'm talking about a male how do I have intricate these haploid sex cells these gametes these sperm cells I'm talking about a female how do I eventually get these OVA these egg cells that have a haploid number and the way that happens is some of these cells up here are going to differentiate into germ cells so they're going to differentiate into germ cells in the case in the case of and and they're going to differentiate it whenever germ cells they're going to differentiate into your gonads in the case of a in the case of a female the gonads are the ovaries are the ovaries ovaries and in the case of a male the gonads are the testes the gonads are the testes and the germ cells in the gonads that or that are or the sales that have differentiated into the being part of the testes and ovaries those germ cells so we differentiate them in we differentiate them from somatic cells so they're germ cells they're germ cells in your ovaries and testes they through the process of meiosis they through the process of meiosis can produce the gametes so if you're a female they're going to produce eggs if your feet if you're male you're going to produce sperm but this is through the process of meiosis meiosis you're going to produce sperm in the case of a man and you're going to produce and you're going to produce OVA in the case of a female and this brings up a really interesting thing because throughout biology we talk about mutations and and a natural selection and whatever else and it's important to realize what mute what mutate how mutations may affect you and your offspring so if you have a mutation in one of the somatic cells here let's say in your in a skin cell or in your brain or in the heart that may affect your ability to you know especially if god forbid it's a really dangerous thing like cancer and it happens when you're young before you've had a chance to reproduce and you're not able to survive that it might affect that might affect your ability to reproduce but if this is happening in a somatic cell it's not going to affect the DNA makeup of what you pass on the DNA makeup of what you pass on that's determined by what's going on in the gametes so mutation if on the way to differentiating into gametes a mutation happens so for if one of these mutate and then keep replicating so let's say there's a mutation here and they keep replicating and they differentiate into the germ cells the mutation is right over there and then through meiosis that produces some mutated sperm then that would pass on to your well that has a chance of passing on to your children because once again it might not be all of the sperm cells that have that mutation it could be only handful of the two to three hundred million of the sperm cells and so if that mutation somehow makes it harder for some of the sperm cells to kind of function either fuse with an egg or even potentially develop and kind of swim through fluid then it still might not be the thing that makes it so mutations mutations only affect your offspring in the situation where those the mutations in the the cells in which they happen are eventually differentiate into things into gametes that you will pass on to your children
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