Meiosis

right today we are going to talk about gametogenesis gametogenesis is the process by which the early germ cells undergo process of meiosis and site or differentiation and eventually convert into mature gamete so what is gametogenesis gametogenesis is a specialized process which occur in the germ cells primordial germ cells and germ cells that these germ cells right they undergo process of meiosis right and meiosis is a special type of cell division which is which occurs in two stages meiosis one and meiosis two and during meiosis chromosome number is reduced to half in the final daughter cells right so meiosis is also called reduction division why we call them your size reduction division because meiosis is a very specialized type of cell division in which after two stages of mitotic divisions the final cells have the chromosomes number half this is it right or we call it reduction division so what is really gametogenesis gametogenesis the process in which the germ cells convert into mature gametes right now in females gametogenesis is called the process of or genesis and in males that gametogenesis process is called the promoter genesis in females during gametogenesis or ho genesis what really happens there female germ cells pass through process of meiosis and then they undergo process of site or differentiation and mature Asian and eventually produce mature gamete which is called mature ovum is the right and in males process of super metal Genest process of gametogenesis in males is called super matter genesis and during super metroid genesis again there is process of meiosis we reduces or chromosome number half in that final daughter cells and processor Sato differentiation which made the maturing germ cells in a final development of mature sperm is that right now first I will go into general concept of meiosis meiosis is occurring in females during oogenesis it is occurring in males during supplemental Genesis so I will discuss first of all muses in some basic detail and after that we will discuss into detail what is the process of oh genesis in female and after that we'll discuss that how the super metal genesis occurs in male so let's first of all discuss about the primary basic concepts of get meiosis now during the process of meiosis let's suppose these are early germ cells for example this is the germ cell if it is in female this must be a ghanaian ah if it is in male then it may be super meta Bonilla to go Nia type B now these are early germ cells and in a religion cell what really happens that let's suppose if I am going to make sperm right then what will happen in my early germ cell which are super meta Gonia there are I have how many chromosomes 46 chromosome in the early germ cells right and these 46 chromosomes 23 I have from my mother right and 23 chromosomes I have from my father so basically how many chromosomes I have 46 chromosomes right so 46 chromosomes are there 46 chromosomes are there and chromosome when there are 46 we call them their diploid number of chromosomes what is this deployed diploid number of chromosomes so what really happens that in early support of Ghanian type b we have how many a male of how many chromosomes 46 chromosomes 23 coming in my case 23 chromosomes must be coming from my mother and 23 chromosomes must be coming from my father so for example it is chromosome number one so this is my chromosome one derived from my mother and this is my chromosome number one derived from my father so and so forth I will wear chromosome number two from mother as well as father chromosome number three from mother and also one copy from father so and so forth so 22 chromosomes will be homologous each other because I have 23 chromosomes from mother and a 23 chromosome from father these are 23 chromosomes are homologous to each other but you have to remember X chromosome in my case must be coming from our mother and Y chromosome must be coming from my father is that right now what really happens if you look at the genetic material amount of DNA remember when we are talking about cell division we have to talk about what is the number of chromosome and we have to talk about what is the amount of DNA in a given cell right now here the number of chromosomes should be measured by the number of centromeres right now in this early cell before it entered into meiosis 1 right this early cell so from otago Nia the number of chromosome with four defects and each chromosome has single structure let me explain this let's suppose this is chromosome from my father and here is chromosome from my mother let's suppose these chromosomes are homologous to each other when I see these chromosomes are homologous to each other it means that both of them are having alleles of the same genetic material for example if it is chromosome number 3 from father paternal then it must be chromosome number 3 from maternal side and if there here is a gene in the DNA of course what is there there must be double-stranded molecule of DNA every chromosome look this is double-stranded molecule of DNA and if these chromosomes are homologous to each other right from all of us to each other I mean chromosome 1 of mother is homologous to the chromosome 1 of the father chromosome number n coming from mother should be homologous to the chromosome number 10 of the father is it right so corresponding chromosomes from mother and father are homologous to each other x and y are not homologous because they are not having the same genetic material right now listen now these are one pair of homologous chromosomes is the right now in this case both chromosomes are having the similar DNA and in the DNA there are genes right what are genes genes a sequence of nucleotides which make a specific functional RNA now let's suppose if there is a gene here right and this gene is about the color of the eye now this gene which is present over here it determines the color of the eye and this gene is coming from the mother then on the same homologous chromosome which is coming from the father and the same locus at the same point there should be gene which also determines the color of the eye and here you suppose another gene which determines the size of the nose from maternal side then on the homologous chromosome coming from paternal side on the same locus right from paternal side there should be gene and this gene should be also determining size of the goes for example here there is a gene which determines structure and function of a specific enzyme right then on the corresponding look locus on the other homologous chromosome there should be a gene which should be responsible for the structure and function of the same enzyme right now these genes these genes which are going to do similar function and they are present on homologous chromosome at the same loci right these genes are in specific relationship to each other as I told you this gene is making a lot of the I maternal hygiene maternal gene for cholera five this is paternal gene for Cairo five both of these genes are alleles of each other what are they they are alleles of each other and what is this gene for the size of the nose the shape of the nose from father side this is the gene for the shape and size of mouth from mother side so these genes that also alleles off each other then if this was a gene from paternal side for a specific enzyme and here on the same locus from the homologous chromosome coming from the mother side also has the same similar gene for the same enzyme then these greens are also alleles the feature that so what we can say when two chromosomes are coming from mother and father is a right and they're having similar genetic material such chromosomes are of homologous of each other and all the homologous chromosome the genes which are having the same loci in their position and doing the similar function right or dictating the similar in from genetic information these genes are what they called alleles this is a right any question up to this no problem now you must remember also one more thing these are the chromosome let us suppose promotion of three paternal this is called single structured chromosome right this is also maternal chromosome but this is also single structure when chromosomes replicate their DNA chromosomes become duplicated let's close this chromosome right it replicated genetic material when the DNA replication will occur what will happen to this chromosome after DNA replication this chromosome will become duplicated is the right in the same way if DNA has been replicated in this maternal chromosome this maternal chromosome will also become yes duplicated now here it is very important and duplicated chromosomes right of course DNA material is double is the right because the has been yes replicated replication of DNA lead to duplication of chromosomal structure or we can use another term now listen this chromosome which does not have replication of DNA this is called it is one chromosome one copy of chromosome number three and it is single structured it is also one chromosome but double structured why because chromosome number is basically counted on the base of Centro Nia is the right centromere is the point where the chromosome is constructed is the right now so this is single structured chromosome this is double structured chromosome single structure chromosome is unreplicated DNA double structured chromosome as replicated DNA this is a right single structured chromosome is also called chromosomes with one chromatid and this is also called one chromosome with two chromatid right or we call this unduplicated chromosome and this is called duplicated chromosome let me recap when DNA when one chromosome has one centromere and one short arm and one long arm what we call that this is unduplicated chromosome ah it is chromosome without a replication or it is single structured chromosome or we can call it chromosome with one chromatid is that right but if this situation is there that DNA of the chromosome has been replicated it is still one chromosome so what we'll call this one chromosome with replicated DNA or we can call it one chromosome with duplicated structure or we call it one chromosome will double structure or we call it one chromosome with two chromatids so I hope you will remember these terms what terms I have made clear in your mind what are the homologous chromosomes and what are alleles on each other is the right homologous chromosomes are homologous alleles and then I talked about what are structured and double structured chromosome in my lecture I will continue such chromosomal structure single structure chromosome and such chromosomal structure I will talk about double structure chromosome any question here no now let's move forward let us suppose that in my body super metal Genesis is going on and if super metal Genesis going on it means my germ cell must be undergoing the process of my germ cell must be undergoing the process of meiotic division which should be an near tip division which is a specialized type of division which occurred specially in formation of germ cells and committed Genesis is the right now let's suppose this is in my test is this is the primary cell of course my testers will not have Omonia right hopefully now we come to super metal Bonilla B now super meta Bonilla be in my body it has 23 then let me write here it has 23 maternal chromosomes 23 maternal chromosomes plus it has how many chromosomes from paternal side also yes 23 paternal chromosome now when there is a full set of 23 chromosome when there is a full set of 23 chromosomes we call it 1n 1 small end so we will choose a term here that in this salad so by matter Bonilla there is number of chromosome one small and from which side the tunnel side one small end from maternal side right one small end is equal to 23 number of chromosome one set of 23 chromosomes now if you put them together right how many ends are there it is two small end and when they are too small then it means it is develop 23 so we can also say that this two small n is 46 chromosomes ah when number of chromosome is too small N or 46 we say it is diploid number of chromosomes what we call it yes diploid number of wide number of chrome I'm talking about this cell which are about to enter into meiosis one now another thing this was about the number of chromosome let's talk about the genetic amount of DNA is it right now amount of DNA this is single structured or double structure single structure chromosome and what is this this is also single structure now come back here in the single structured chromosomes if there are 23 see 23 chromosomes which are single structured 23 chromosomes which are single structured we call it the amount of DNA is one capital n capital n is notation used for the amount of DNA in a given cell small n is the notation which is used to the number of chromosome now if we talk about there are 23 paternal chromosome single structure what we will say that there are 1n paternal chromosome and one end mean 23 chromosomes and I say one capital and also right this is not only one small n it is one small n and it is one capital n now when I say it is one small n situation it means that 23 paternal chromosomes and if I say one capital n it means it is single all 23 chromosome the single structure what is this single chromatid a single structure or single chromatids chromosomes is that right now in the same way these two chromosomes I have drawn here right again in this maternal side how many chromosomes from maternal side there again one end from with terminal side so 23 chromosomes set from maternal side and each chromosome is double structured finger of structure here single structure so it will be one and single structure is it right so in this case what we will say that put one small n plus one small and so what is the number of chromosome too small and or we can say what is the number of chromosomes total 46 so this cell has 46 total number of chromosome and diploid cell but look at the DNA of it it has one 23 23 single structured from paternal side it has 23 single structure chromosome from maternal side so one end from it along side this is amount of DNA so amount of DNA from mother is one n amount of DNA from father is one end so how many capital and amount of DNA - is that right any question up to this no now we come to this situation actually what happened before this cell is entering into meiosis one if before this cell enter into meiosis one it is going to replicate its DNA and all chromosome paternal chromosome as well as all the maternal chromosomes they will replicate DNA and all the DNA is replicated all the chromosomes will become double structured chromosome what they will become double structured chromosome it means when these single chromosomes will become double structured chromosome here so these structures will convert into this type so it means every chromosome either double structure now this cell with double structured chromosomes right this is called yes what is the sky it is called primary gamete what is it what it is called primary gamete of course this primary gamete in female it will be primary oocyte and of course I am NOT female so it will be primary so format aside is the right now in the primary spermatocyte which is derived from so far Motoko nia be or the female primary oocyte which are derived from all Gonia right they are having double structured chromosome because they have already replicated and if they have already replicated their DNA very carefully we'll talk about this structure right how many chromosomes paternal chromosomes are there now we have 23 paternal chromosome but double structured here were 23 paternal chromosomes single structure so what will say that paternal chromosomes are 23 how many paternal chromosome our paternal chromosomes at 23 and how many N 1 1 small n this is right and Plus on paternal side maternal side yes but how many look at this cell there were 23 signo structured and here there are 23 double structured so we'll again right 23 but double structured maternal chromosomes is that right and how many small and it is there it is still one small and because even though they're double structured but actually the number of chromosome depends on number of centromeres this is it right so how much it will make both of them together total chromosome will become 2n small or we can say total number of chromosome will be yes no it will be still deprived this cell in the beginning will be still diploid but there's very important thing amount of DNA has been doubled here right because every chromosome from here to here or from here to here has become double structure now if we are talking about the amount of DNA now here the amount of DNA was 2 N 1 and was contributed by father and paternal chromosomes and 1n was contributed by the maternal chromosome was a right and in the same way here now 1n has become 2 n so 2 and in paternal set of 23 chromosomes so we can say that paternal this is actually to capital n amount of DNA here it is how much to end because it is all through a double structure so total and will be how much for n so we can say that primary gametes frame the gametes mean and males primary spermatocytes and in females primary oocyte right all the chromosomes from maternal and paternal side are double structure chromosome and but number of chromosomes still remain deployed is the right and but amount of DNA has become double is it right any question here right I'm just going to take your test because this bothers a lot to the students right this concept and then we'll move forward right yes this is the early germ cell right how many it is how many number of chromosomes two men right one and from father one and from mother this is the number of chromosome so it is equal to 46 right it is equal to die pride situation time provide situation this is that right but we talked about the what is this genetic material from mother the amount of DNA is one N one capital n from maternal side plus one capital and from paternal side so mount of DNA is to capital n any question here no problem now this cell convert into primary Gandy eight right but before that this cell has to replicated this DNA and every chromosome has become double structured all with a run in parallel chromosomes now number of chromosome number of chromosome remains the same because centromere the same but each chromosome has become double structured or duplicated a double chromatin chromosomes right so what will right here number of chromosome to small line to small and is equal to still 46 is still tight right is there right but the real thing to understand here amount of DNA has been developed because amount of DNA has been doubled so this one amount of DNA here was one hand and one end now it has become 2 n + 2 n so what is the amount of DNA is equal to 4 n any question here it's clear after these some fundamental concept now we come to some special processes which occur in meiosis 1 right there are some processes which occur in meiosis 1 and these processes do not occur during mitosis what is that listen the homologous chromosomes during in yourself homologous chromosome which have from mother and father they are lying in the nucleus randomly they are lying in the nucleus randomly right for example chromosome coming from your mother chromosome number 7 and chromosome number 7 coming from your father they are lying injured nuclei randomly that's right when mitosis occur during mitosis now all chromosome replicate their DNA and become double structure but double structured chromosome during mitosis the homologous chromosome don't come near to each other and don't pee read each other what does it mean that let's suppose if in my body a skin cell is under way in the process of mitosis then chromosome number 7 from my mother and chromosome 2 salmon from a father will become double structured during mitosis but they will not come close to each other they will never pair with each other they will never do talk to each other they will never you can say to exchange material with each other but during meiosis something very special and what is that that is that homologous chromosomes from maternal side and paternal side they come together and pair with each other right the special thing is the pairing occurrence pairing mean that let's pose this is maternal chromosome number double structure chromosome number one here is maternal chromosome number two here is maternal chromosome number three you will be so surprised you should be really surprised and apprec-- what goes on at biological and molecular level that maternal chromosome number one will look where is the paternal chromosome one in the same nucleus homologous chromosomes from mother and father start coming together look where the other partner is so what really happens that at this stage at next stage these double structure homologous chromosome look for their homologous partner so chromosome number one from mother will pair itself with chromosome number one from father and chromosome number two from mother will pair itself with the chromosome number two from father right paternal paternal and chromosome 3 which is mother it will pair itself I don't know how they really look but anyway they do it right so chromosome number three from patellas and so and so forth the spearing continues from homologous double structured chromosome to the homologous double structured chromosome from 1 to 22 is they right at all the autosomes and in the end of course if it is going on in female it will be X and X chromosome come together but if it is the male during spermatogenesis then X from maternal side and Y which was coming from a father they will also come together and they have few homologous genes right on short arms right so what really happens that maternal homologue double structured homologous chromosomes during the Meuse is 1 and paternal now here is one I'm going to explain up to this here I will come to me Oh sis - so first stage of meiosis chromosomes maternal and paternal ah already double structured these homologous chromosome look for the homologous partner and every Humalog of chromosome pair itself right here itself lengthwise point to point with the homologous chromosome why they are coming together they have to do something you know they are going to talk and make special work for the next remember in your somatic cells but Terrell chromosomes and paternal chromosomes even don't talk to each other they are randomly doing the they are randomly lying in the nucleus but doing their function only during gamete Oh Genesis it's a matter of next generation so in my body chromosome from my mother and father chromosome one from a mother and father they will close come together and in my wife's body doing organicist chromosome number one from her mother and chromosome one from her father will come together this is their right and what will happen then those chromosomes which come together and make pairs right this pairing point-to-point making the pairing this process is called what is this called synapses so what what these chromosomes are doing they are making point-to-point their matching will call this is a process of synapse --is a process of pairing of the homologous chromosome after that what they do these chromosome who wants they have made pairs you know what they do they start exchanging that blocks of genes with each other they start exchanging the blocks of genes with each other let me enlarge this for you for example this pair I enlarged and what really happens there this is maternal chromosome number three and now paternal chromosome well six there will become very intimate you know I don't know what they are doing at molecular level but what biologists claim now what they are going to do they will exchange the blocks of genes you know one chromosome has thousands of the genes right of course this is having DNA molecule it has alpha DNA molecule these DNA molecules will come together of course as chromosome come together and they exchange the alleles with each other right and then they are exchanging the alleles and they are exchanging the blocks of genes we say they are crossing so it's not only mother and father cross even for the next generation in our body when gametogenesis going homologous chromosomes also cross with each other and exchange their genetic material or shuffle their genetic material to add the diversity to the future generation now so this process where they come together and eventually start crossing the material and exchanging the genetic material with each other which I've shown here this process is called crossing over so crossover occur remember this crossing over or exchange of genetic material or blocks of genes between the two homologous chromosomes specially occurs in meiosis it does not occur in mitosis is that right now how many such couples will be made there 23 is there right how many changes will be going on and how many chromosomal pairs 23 pairs all pairs will be exchanging some material with each other they say somewhere 30 to 40 crossover occur right in whole the maternal and paternal set of chromosomes do you understand it so after the crossing over has been done they will become separate but they have exchanged from genetic material and when they will become separate from each other look now they are going away from each other but look here what has happened one piece off yes paternal one piece of paternal genetic material has been exchanged with maternal chromosome right so now this maternal chromosome has some paternal genes and this paternal chromosome has some maternal jail so this maternal chromosome is after the cross over after the cross over when the separate from each other maternal chromosomes are purely maternal sorry paternal chromosomes are not purely maternal they do have some maternal material and maternal chromosomes are not purely maternal they do have some paternal material they you understand it now when this chromosomes will go away they have made a unique recombination right this was maternal genetic material this was paternal they come near make synapses and then the crossover and exchanges and when they're separating from each other maternal chromosomes have recombined their material with some of the paternal and vice-versa and when they're separating with each other they make this from crossing over point they are still attached but rest of the chromosome couple is going away right this situation is called formation of Kozma what it is called formation of Kozma so these specially these are the very special and unique features which occur in meiosis first meiotic division which did not occur in mitosis what are these special number one process of synapses where homologous chromosome pair with each other secondly process of crossover where homologous chromosome exchange the blocks of genes with each other right and to add the genetic diversity for the future generation and then when they're separating under the microscope they look like a very special arrangement right crossing each other and when they're getting separate from each other this is called a Ozma is the right these three features are not seen in yes mitosis any question here even if the parents are divorce this thing will happen that's the beauty there's molecular level we are more committed than the social level for example my mother and father if they are divorce it doesn't matter even if they have died now but in my test is the chromosomes which came from a mother and chromosome came from a father they are still today right talking to each other before they make the spawns for the next generation is the right i--i chromosomes don't fight yes that's right Rama songs don't fight right now listen what we have done we are talking about first meiotic division we started with the primary gamete in males with primary so for meta fights in females with primary oocyte right DNA's DNA material is double structured chromosomes are 46 double structured chromosome with 4n material foreign genetic DNA then what happen homologous chromosomes make pairs then the crossover synapses and crossover and eventually the separate but now they exchange some material with each other and what is this going on k Ozma and next step is alignment that these chromosomes will align themselves on spindle right so the next step is alignment alignment now at the time of line meant how many sets will align on the chromosome on the spender 23 double structured which were originally in maternal and 23 double structure which were originally maternal and 23 double structured which are originally paternal right of course they are now having some recombination then what will happen these maternal and paternal 23 chromosome right they will be assaulted randomly and going towards the they will go away towards what is there to daughter cell here it is very important let me tell you when these chromosomes are going away at this stage for example this is they are now going to assault suppose this is chromosome number one here is the set of chromosome number two here is the set of chromosome number three but of course you should not forget that there are some crossover already going on is there right now the maternal are not purely maternal and paternal are not purely Patera is that right now for example this is chromosome number one set this is chromosome number two this is chromosome number three when they will move as here they are moving their 23 sets paternal and 26 paternal but local for example this is one first daughter South and here is the second daughter her first daughter cell may get chromosome one from mother chromosome number two from father crows song number three from mother so they're randomly getting maternal or paternal devil structure chromosome and salable to daughter cell number two will get chromosome number double structure chromosome number one from father to mainly from mother and three mainly from father so what really happens that when after alignment right the chromosomes will double structure chromosome will disengage with each other these homologous chromosome this what is this disconnect from each other right and then they'll right now this disjunction what is this when their disjunction with each other right when the disjunction with each other they are randomly assorted and allocated to the daughter cell they are randomly allocated it's quite possible this daughter cell number one here may have maternal chromosome number ten with some paternal material and paternal chromosome number eleven is somewhat under this is right do you got it so that was another way to add the genetic variability right due to random assortment and allocation of double structured homologous chromosomes which have gone under the process of crossover so up to now by two mechanism genetic variability is the crane number one exchange of genetic material in between the homologous chromosomes secondly random assortment of homologous chromosomes to the daughter cells and eventually when daughter cell is produced here at the end of the first meiotic division these two daughter cells are called which gotta sell these daughter cell that no more primary gamete they are now called secondary gamete what are these here we had yes primary gamete here will have secondary gamete now ii get a secondary gamete of course either it is in males it will be secondary so for meto site and in females it must be secondary Oh site but in case a female this will become secondary your site and other daughter cell will get very little cytoplasm so other daughter cell is called first polar body in males both of them will be called secondary super metal sites secondary gametes in the male their secondary spermatocytes but in females there are two cells which result as secondary gamete one cell which get almost all the cytoplasm is secondary ovum and other cell which gets a very little cytoplasm that is called first polar body this is the right but let's get a complete set of 23 chromosomes right now let's see what is the situation they are after it will give Ian now this cell again remember when did nan when disjunction occurred here sorry it was not nan distinction when they separate from each other this was disjunction when disjunction here centromeres don't divide these are the homologous pairs which go from each other right to the daughter cell homologous chromosomes pair which go to the daughter cell randomly now in this cell secondary suppose gamete it is one end what is that one end but it's single structure double structure it is double structured one end for how many double structure chromosome 23 chromosome but double structured right this should we call now yes this should be called 1m or 23 chromosome but this is double structured so we can also call it apply it now applied number of chromosome is there right so what we can say in the same way this from this cell secondary gamete it does how many chromosome 23 but double structure right so it is also how much now one small n 23 chromosomes double structured and haploid number of chromosomes but amount of DNA is double is a right because every chromosome is double structure this is the right so what we'll call it it is 2n DNA right 23 double structure here is also 2 n so what will say this is 23 chromosome each chromosome is double structured due to that reason it is one small and right or it is called applied is the right applied but when you talk about amount of DNA it is 2 and why it is to end even though chromosomes are 23 you may think it may be one end but because every chromosome has double structured so development of DNA so it's 2 n this is that right now here I want you to be very clear when the beginning of the muses primary gamete are at the beginning of the muses and one primary game it gives second recommit at the end of first meiotic division at the end of first period in the beginning how many chromosomes were there 46 the worst structure so there were diploid cells with 4n here are 23 but double structure so haploid number of chromosomes but 2n does it right so this complete of our first meiotic division after the first meiotic division these cells do second meiotic division but when they enter indirectly enter into second we are taken to be on without replicating their DNA further so this 23 chromosomes which are double structured at next stage just their centromeres disjunction what breaks down separating of the centromere and when their centromeres break down each chromatid go to other side this was double structure chromosome and out of every double structured chromosome one structure go to one side and other structure go to the other daughter cell right so it means double structure chromosomes or chromosome with two chromatid supplied at the centromere point and here centromere break down right here only homologous chromosome are going away in during meiosis one in meiosis two centromeres will break down and double structured chromosome one double structure chromosome will convert into to sing of structure and chromosomes which go to the opposite pole and go to the daughter cell now how many single structure devil structure chromosome were here 23 double structure they will eventually rail down into 2346 what single structure 23 will go on one side and 23 will go to other side and same will occur with other cell also that this number which is haploid cells right but double structure they will again breakdown in the centromere and single structured chromosome will go to the ends now these are the final product of second meiotic division right at the end of the second we are to do BN right we were having at the sorry in the beginning of second we are till to b and b we are having how many secondary damage to secondary damage and how much much a final Selda produced for self right now in this case these four daughter cells which are produced at the end of the second meiotic division every cell has how many chromosomes 23 chromosome so every cell has 23 single structure 23 chromosomes which are single struck child right so it should be one small end or we can say this is just number is applied what is it applied but if you talk about amount of DNA here what are how much is that one end is right so in all these four cells which are produced as a result of the second meiotic to be and all these four cells will have applied number of chromosome every chromosome it's single structure but every chromosome may be slightly different from other chromosome due to crossover and random assortment and amount of DNA s1n is that right now advantage of this is by the end of the aortic divisions first and second every germ cell sperm or ovum is having haploid number of chromosome so my sperm will provide haploid number of chromosomes and my wife over on the lasso brain applied number of chromosomes and when they were fused together in the zygote after fertilization zygote formation will be reestablishment of diploid number of chromosomes am i clear any question here yeah what is that at this stage what happens to female / Genesis also permit a Genesis let me explain in supplemental Genesis what happens that one primary in spermatogenesis one primary gamete which is primary super metal site divides at the end of first mutant division into two secondary super metal site and then each secondary super metal side divided into two spermatid which eventually mature into two spawns so because to spawn will come from this secondary gamete super metal site and two will come from this so in male from one primary gamete how many secondary gamete are made for all of them become mature spawn but in female there's the little difference the difference is that one primary gamete during first meiotic division when it makes two cells one cell will get all the cytoplasm and this cell is called secondary oocyte other cell will get very little cytoplasm and that is called first polar body then in female when secondary gamete is going to be mature ovum then praying a secondary oocyte secondary oversight divided into two cell one cell takes all the cytoplasm so this cell with 23 single structured chromosome and all the cytoplasm this is called definitive ovum or mature and other is called second polar body is the right which is the second daughter cell which is getting almost no cytoplasm meanwhile this first polar body also divided into two cells and they are also called throughout a fourth polar body so we can say that actually what happens in female out of the four what is this for final daughter cells one become definitive over and three are polar bodies and the difference in polar body indefinitely is definitely going that's all most all the cytoplasm polar body get very little cytoplasm and they did generate the right they are not functionally is useful right now if someone asked you that what is the purpose of meiosis meiosis is a very specialized type of cell division which occur in the germ cell to make the mature German native cells and males they make spawns and the females will make over is that right during meiosis has two stages first stage and second stage of meiosis does the right now during meiosis during first step of meiosis some special events occur number one homologous chromosomes pair with each other synapses then homologous chromosomes cross over in exchange genetic material and then they're separating from each other and making structure of casma and eventually they align themselves and they separate from each other but remember the centromeres do not break down this is first meiotic division in the beginning of the first meiotic to be and we have which cells primary gave me it's at the end of the first quadrant we will be a secondary gamete primary gametes are 46 chromosomes double structure for and DNA material second we have each half 23 23 chromosomes and which are also double structured and 2n genetic material in each daughter's house is that right then when these secondary gamete go to the second meiotic do beyond simply these cells do not go into interface because in interphase DNA replication should occur but they do not go into interphase cells from second first meiotic Dominion directly going to second meiotic division without replicating their DNA but what they do double structure chromosome break apart at center-right centromeres and in those structures or single chromatid go to the daughter cells each single chromatid from the double structure to chromosome go to the cell and two secondary gamete eventually made for final daughter cells any question to have diversity diversity genetic diversity is assured during these steps number one than genetic diversity occur the next generation number one due to crossing over where genetic blocks of genes are exchanged number two genetic there were still further insured the random assortment of maternal and paternal homologous chromosome to the daughter cells during first meiotic division and in the end third mechanism of genetic diversity come when yes genetic material from spawn and genetic material from the ovum fused with each other they are having different combination and and which will come with unique genetic makeup any question here there's no question let's celebrate

Channel: Dr. Najeeb Lectures

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Keywords: meiosis, meiosis definition, mitosis y meiosis, meiosis stages, meiosis 1, stages of meiosis, meiosis and mitosis, que es meiosis, meiosis y mitosis, meiosis vs mitosis, phases of meiosis, meiosis 2, difference between meiosis and mitosis, meiosis phases, meiosis fases, meiosis 1 and 2, meiosis animation, steps of meiosis, meiosis cell division, meiosis video, meiosis mitosis, meiosis steps, meiosis crossing over, meiosis process, embryology, dr najeeb lectures

Id: D_2xGUVUGw4

Length: 51min 52sec (3112 seconds)

Published: Mon Mar 19 2012