0:03 right today we are going to talk about GTO Genesis gametogenesis is the process by which the early germ cells undergo process of meosis and CYT differentiation and eventually convert into mature gamet 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 meosis right and meosis is a special type of cell devian which which occurs in two stages meosis one and meosis 2 and during meosis chromosome number is reduced to half in the final daughter
0:50 cells right so meosis is also called reduction division why we call meis reduction division because meosis is a very specialized type of cell devian in which after two stages of miotic devian the final cells have their chromosomes number half is that right or we call it reduction divion so what is really gametogenesis gametogenesis is a process in which the germ cells convert into mature gametes right now in females gametogenesis is called the process of oogenesis and in males the gametogenesis process is called suat Genesis in females during gametogenesis or
1:35 oogenesis what really happens that female germ cells pass through process of meosis and then they undergo process of CYT differentiation and maturation and eventually produce mature gamut which is called mature ovam is that right and in males process of suenes process of gametogenesis in males is called spermatogenesis and during spermatogenesis again there is process of meosis which reduces a chromosome number half in the final daughter cells and process of CYT differentiation which make the uh maturing germ cells in a final development of mature sperm is
2:21 that right now uh first I will go into General concept of meosis meosis is occurring in females during o is it is occuring in males during stomatogenesis so I will discuss first of all mosis in some basic detail and after that we'll discuss into detail what is the process of oogenesis in female and after that we'll discuss that how the superat Genesis occurs in male so let's first of all discuss about the primary basic concepts of G meosis now during the process of meosis let's suppose these are early germ cells for example this is a germ cell if it is in female this must be o gonia or if it is in male then it may be supermat
3:11 gonia spermato gonia type B now these are early germ cells and in early germ cell what really happens that let's suppose if I'm going to make sperm right then what will happen in my early germ cell which are Super metonia there are I have how many chromosomes 46 chromosome in the early germ CS right and these 46 chromosome 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
4:01 and chromosome when they are 46 we call them their diploid number of chromosome what is this died Diplo number of chromosomes so what really happens that in early spat gonia type B we have how many a male have how many chromosomes 46 chromosome 23 coming in my case 23 chromosomes must be coming from a mother and 23 chromosom must be coming from my father so for example it is chromosome number one so this is my chromosome number one derived from my mother and this is my chromosome number one derived from my father so and so forth I will have chromosome number two from mother as well as father chromosome number three from mother and also one
4:48 copy from father so and so forth so 22 chromosomes will be homologous to each other because I have 23 chromosomes from mother and I 23 chromos from father these all 23 chromosomes are homologous to each other but you have to remember X chromosome in my Cas must be coming from my 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 divion 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 chromosom should be measured by the
5:34 number of central me right now in this early cell before it enter into meosis one right this early cell so pronia the number of chromosome is 46 and each chromosome has single structured let me explain this let's suppose this is chromosome from my father and here is chromosome from my mother 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 Le of the same genetic material for example if it's chromosome number three from father paternal then it must be chromosome number three from maternal side and if
6:20 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 standard molecule of DNA and if these chromosomes are homologous to each other right homologous to each other mean chromosome one of mother is homologous to the chromosome one of the father chromosome number 10 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're not having the same genetic material right now listen these are one pair of homologous chromosome is that right now in this case the both chromosomes are having the
7:08 similar DNA and in the DNA there are genes right what are genes genes are 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 at the same Locus at the same point there should be Gene which also determines the color of the eye and here is suppose another Gene which determines the size of the nose from maternal side then on
7:53 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 nose for example here there's a gene which determines structure and function of a specific enzyme right then on the corresponding Lo 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 look these genes which are going to do similar function and they are present on homologous chromosome at the same locai right these genes are in specific
8:42 relationship to each other as I told you this Gene is making color of the eye maternal side Gene maternal Gene for color of eye this is paternal Gene for color of eye both of these genes are Al of each other what are they they are Al of each other and what is this Gene for the suppose size of the nose or shape of the nose from Father's Side this is the gene for the shape and size of nose from mother's side so these two genes are also Al of each other then if this was a gene from paternal site for a specific enzyme and here on the same Locus on the homologous chromosome coming from the mother side also has the same similar Gene for the same enzyme then these genes are also aled of each
9:27 other so what we can say when two chromosomes are coming from mother and father is that right and they're having similar genetic material such chromosomes are homologous of each other and on the homologous chromosome the genes which are having the same Loi in their position and doing the similar function right or dictating the similar in genetic information these genes are what they called SE is that right any question up to this no problem now you must remember also one more thing these are the chromosome let us suppose chromosome are three paternal this is called single structured chromosome right this is also maternal
10:15 chromosome but this is also single structured when chromosomes replicate their DNA chromosomes become duplicated let's suppose this chromosome right it replicate genetic material when when the DNA replication will occur what will happen to this chromosome after DNA replication this chromosome will become duplicated is it 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 in duplicated chromosomes right of course DNA material is double is that right because DNA has been yes replicated replication of DNA
11:04 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 central m is that right centromere is the point where the chromosome is constructed is that right now so this is single structured chromosome this is double structured chromosome single structured chromosome
11:50 is unreplicated DNA double structured chromosome as replicated DNA is that right single structured chromosome is also called chrom chromosome 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 or it is chromosome without replication or it is single structured chromosome or we can call it chromosome with one chromatid is is that right but if this situation is there the DNA of the chromosome has been replicated it is still one chromosome so
12:36 what will call this one chromosome with replicated DNA or we can call it one chromosome with duplicated structure or we call it one chromosome with double structure or we call it one chromosome with two chromatids so I hope you will remember these terms what terms I made clear in your mind what are the homologous chromosomes and what are Al on each other is that right homologous chromosomes have homologous ales and then I talked about what are single structured and double structured chromosome in my lecture I will continue such chromosomal structure as single structured chromosome and such chromosomal structure I will talk about double structured chromosome any question here no now let's move forward let us suppose that in my
13:22 body superat Genesis is going on and if superat Genesis going on it means my germ cell must must be undergoing the process of my germ cell must be undergoing the process of miotic divion which divion neotic division which is a specialized type of division which occur especially in formation of germ cells and kenesis is that right now let's suppose this is in my testes this is the primary cell of course my testes will not have oogonia right hopefully now we come to sagonia B now sagonia B in my body it has 23 let me write here it has 23 maternal chromosomes 23 maternal chromosome plus
14:10 it has how many chromosomes from paternal side also yes 23 paternal chromosome now when there's a full set of 23 chromosome when there's a full set of 23 chromosome we call it 1 n one small n so we will use a term here that in this cell so Veronia there is number of chromosome one small n from which side paternal side one small n from maternal side right one small n is equal to 23 number of chromosomes one set of 23 chromosomes now if you put them together right how many n's are there it is two small n and when they're two
14:57 small n it means it is double of 23 so we can also say that this two small n is 46 chromosomes or when number of chromosom is too small n or for6 we say it is diploid number of chromosome what we call it yes diploid number of loid number of chromosome I'm talking about the cell which is about to enter into meosis one now now another thing this was about the number of chromosome let's talk about the genetic amount of DNA is that right now amount of DNA this is single structured or double structured single structured chromosome
15:43 and what is this this is also single structured now come back here in the single structured chromosomes if there are 23 23 chromosomes which are single structured 23 chromosomes which are single structured we call it the amount of DNA is 1 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 structured what we will say that there are one n patal chome and 1 n mean
16:32 23 chromosomes and I say one capital N 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 there 23 paternal chromosomes and if I say one capital N it means it is single all 23 chromosomes are single structured what is this single chromatid or single structured or single chromatids chromosomes is that right now in the same way these two chromosomes I have drawn here right again it's maternal side how many chromosomes from maternal side there are again one and from Eternal side so 23
17:17 chromosomes set from Eternal side and each chromosome is double structured single structured here single structured so it will be 1 n single structured is that right so in this case what we will say that one small n plus one small n so what is the number of chromosome 2 small n or we can say what is the number of chromosomes total 46 so this cell has 46 total number of chromosome and diolite cell but look at the DNA of it it has 23 23 single structured from paternal side it has 23 single structured chromosome from maternal side so 1 n from maternal side this is amount of DNA
18:03 so amount of DNA from mother is 1 n amount of DNA from father is 1 n so how many capital N amount of DNA 2 N is that right any question up to this no now we come to this situation actually what happened before this cell is entering into meosis one before the cell enter into meosis one it is going to replicate its DNA and all chromosome paternal chromosome as well as all maternal chromosomes they will replicate DNA when 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
18:50 structured chromosome here so these structure will convert into this type so it means every chromosome is a double structured now this Cell Double structured chromosomes right this is called G yes what is this called it is called primary gamet what is it what it is called primary gamet of course this Primary gamet in female it will be primary oite and of course I'm not female so it will be primary spaty is that right now in the primary supertoy which is derived from supper metonia b or in the female primary o site which are derived from oronia right they are having double
19:37 structured chromosome because they have already replicated their DNA and if they have already replicated their DNA now very carefully we'll talk about the structure right how many chromosome paternal chromosomes are there now we have 23 paternal chromosome but double structured here were 23 paternal chromosome with single stru structured so what will say that paternal chromosomes are 23 how many paternal chromosome are paternal chromosomes are 23 and how many n One n one small n is it right and plus on paternal side uh maternal side yes maternal are how many look at this cell
20:23 there were 23 single structured and here there are 23 double structured so we will again write 23 but double structured maternal chromosomes is that right and how many small n it is there it is still one small n because even though they're double structured but actually the number of chromosome depends on number of croas is that right so how much it will make both of them together total chromosome will become small 2 and small or we can say total number of chromosome will be yes no it will be still Diplo this cell in the beginning will be still Diplo but there's a very important thing amount of DNA has been doubled
21:10 here right because every chromosome from here to here or from here to here has become double structured now if you're talking about the amount of DNA now here the amount of DNA was 2 N One n was contributed by father and paternal chromosome chromosomes and one n was contributed by the maternal chromosome is that right and in the same way here now 1 n has become 2 N so 2 N 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 again 2 N because it is also double structured so total n will be how
21:57 much 4 4 n so we can say that primary gametes primary gametes mean in males primary super sides and in females primary oite right all the chromosomes from maternal and paternal side are double structured chromosome and but number of chromosomes still remain diploid is it right and but amount of DNA has become double is it right any question here right I'm just going to take your task because this bothers a lot to the students right this concept and then we'll move forward right yes this is the uh early germ cell right how
22:42 many it is how many number of chromosomes 2 N right one n from father one n from mother this is the number of chromosome so it is equal to 46 right it is equal to dipl situation Di situation is that right but we talk about the what is this genetic material from mother the amount of DNA is 1 n 1 capital N from maternal side plus 1 capital N from pnal side so amount of DNA is 2 capital N any question here no problem now we this cell convert into primary gamit right but before that this cell has
23:30 replicated this DNA and every chromosome has become double structured all maternal and paternal chromosomes now number of chromosome now number of chromosome remain the same because centr are the same but each chromosome has become double structured or duplicated or double chromed chromosome right so what we will write here number of chromosome two small n two small n is equal to still 46 is still diploid is that right but but the real thing to understand here amount of DNA has been doubled because amount of DNA has been doubled so this was amount of DNA here was 1 n and 1 n now it has become 2 N and 2 N so what is the amount of DNA is equal to 4N any question here
24:18 it's clear after these some fundamental concepts now we come to some special processes which occur in meosis one right there are some processes which occur in meosis one and these processes do not occur during mitosis what is that listen the homologous chromosomes during in your cells homologous chromosome which are from mother and father they are lying in the nucleus randomly they're lying in the nucleus randomly right for example chromosome coming from your mother chromosome number seven and chromosome number seven coming from your father they're lying in your nuclei randomly does it right when mitosis occur during mitosis now all chromosome
25:04 replicate their DNA and become double structured but double structured chromosome during mitosis the homologous chromosome don't come near to each other and don't pair with each other what does it mean that let's suppose if in my body a skin cell is undergoing the process of mitosis then chromosome number 7even from my mother and chromosome number seven from my father will become double structured during mitosis but but they will not come close close to each other they will never pair with each other they will never do talk to each other they will never uh you can say uh exchange material with each other but during meosis something very special occur what is that that is that homologous chromosomes
25:49 from maternal side and paternal side they come together and pair with each other right the special thing is the pairing occur pairing mean that let's suppose this is maternal chromosome number double structured 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 appreciate what goes on at biological and molecular level that maternal chromosome number one will look where is the paternal chromosome number one in the same new nucleus homologous chromosomes from mother and father start coming together look where the
26:36 other partner is so what really happens that at this stage at next stage these double structured 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 self with the chromosome number two from father right paternal paternal and chromosome number three 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 paternal and so and so forth this paing continues from homologous double structured chromosome to the homologous double
27:23 structured chromosome from 1 to 22 is that right 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 in male during spat Genesis 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 homolog double structured homologous chromosomes during the meosis one and paternal now here meosis one I'm going to explain up to this here I will come to meosis 2 so first stage of meosis chromosomes maternal and paternal are already double structured these
28:08 homologous chromosome look for their homologous partner and every homologous chromosome pair itself right pair itself lengthwise point to point with the homologous chromosome why they're coming together they have to do something you know they are going to talk and make special work for the next generation remember in your somatic cells maternal chromosomes and paternal chromosome even don't talk to each other they randomly doing the they're randomly lying in the nucleus but doing their function only during citogenesis it's a matter of Next Generation so in my body chromosome from my mother and father chromosome one from my mother and father they will close come together and in my wife's body
28:55 doing o Genesis chromosome number one from her mother and chromosome number one from her father will come together is that 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 synapsis so what what these chromosomes are doing they're making point to point they're matching so we call this is a process of synapses or process of pairing of the homologous chromosome after that what they do these chromosome once they have made pairs you know what they do they start exchanging the blocks of genes with each other they
29:41 start exchanging the blocks of genes with each other let me enlarge this for you for example this pair I enlarge and what really happens there this is maternal chromosome number three and now paternal chromosome will six they 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 uh this is having DNA molecule it has also DNA molecule these DNA molecules will come together of course as chromosome come
30:27 together and they exchange the AL with each other right and when they are exchanging the Al and they're exchanging the blocks of genes we say they are crossing over so it's not only mother and father cross even for the Next Generation in our body when gito Genesis 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 with they come together and eventually start crossing the material or 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
31:14 blocks of genes between the two homologous chromosome especially occurs in meosis it does not occur in mitosis is that right now how many such couples will be made there 23 is that right how many exchanges 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 and hold 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 a change some genetic material and when they will become
32:00 separate from each other look now they're going away from each other but look here what has happened one piece of 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 Gene so this maternal chromosome is after the crossover after the crossover when they separate from each other maternal chromosomes are not purely maternal and sorry paternal chromosomes are not purely maternal they do have some maternal material and maternal
32:45 chromosomes are not purely maternal they do have some paternal material do 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 they cross over 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 still attached but rest of the chromosome couple is going away right this situation is called formation of kosma what it is called formation of of kma so these spe these are the very
33:32 special and unique features which occur in meosis first metic division which do not occur in mitosis what are these special number one process of synapsis 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 chasma is it right these three features are not seen in yes mitosis any question here even if the parents are divorced this these things
34:19 happen even if the parents are divorced this thing will happen that's a beauty the 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 spun for the next generation is that right oh yeah chromosomes don't fight yes that's right chromosomes don't fight right now listen what we have done we are talking about first mtic division which started with the primary gamit and M with primary subite and females with primary
35:07 oite right DNA DNA material is double structured chromosomes are 46 double structured chromosome with 4N material 4N genetic uh DNA then what happen homologous chromosomes make pairs then the crossover synapsis and crossover and eventually they separate but now they have exchanged some material with each other and what is this going on chasma and next step is alignment that these chromosomes will align themselves on spindle right so next step is alignment alignment now at the time of alignment
35:55 how many sets will align on the chromosome on the SP 23 double structured which were originally 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 assulted randomly and going towards the they will go away towards what is the there to daughter cell now 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
36:42 going to assort suppose this is chromosome number one here is the set of chromosome number two 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 that right now the maternal are not purely maternal and paternal are not purely paternal is it 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're moving that 23 sets paternal and 26 paternal but look for
37:28 example this is one first daughter cell and here is the second daughter cell first daughter cell may get chromosome number one from mother chromosome number two from father chromosome number three from mother so they're randomly getting maternal or paternal double structured chromosome and cell number two daughter cell number two will get chromosome number double structured chromosome number one from father two mainly from mother and three mainly from father so what really happen happens that when after alignment right the chromosom will double structured chromosome will disengage with each other these homologous chromosome this what is this disconnect from each other right and then they right now this disjunction
38:15 what is this when they disjunction with each other right when they disjunction with each other they are randomly assorted and allocated to the daughter cell they're randomly allocated it's quite possible this daughter cell number one here may have maternal chromosome number 10 with some paternal material and paternal chromosome number 11 with some maternal material is that right did 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
39:02 occurring number one exchange of genetic material in between the homologous chromosome secondly random assortment of homologous chromosomes to the daughter cells and eventually when daughter cell is produced here at as at the end of the first metic division these two daughter cells are called which daughter cell these daughter cells are no more primary gamet they are now called secondary gamet what are these here we had yes primary gamut here we will have secondary gamut now in second secondary gamet of course either it is in males it
39:47 will be secondary supery and in females it must be secondary oite but in case of female this will become secondary oite 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 suyes secondary gametes in the M are secondary supery but in females the two cells which result as secondary gamet one cell which got almost all the cytoplasm is secondary ovam and other cell which gets a very little cytoplasm that is called first polar body is that right but it's got a complete set of 23
40:34 chromosomes right now let's see what is the situation there after the divion now this cell again remember when there non when disjunction occur here sorry it was not non disjunction when they separate from each other this was disjunction when disjunction here centrom 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 gamit it is 1 n what is it one n but it's single structured double structured it is
41:19 double structured One n for how many double structured chromosome 23 chromosome but double structured right this should be called now yes this should be called 1 n or 23 chromosome but this is double structured so we can also call it helide now hli number of chromosome is it right so what we can say in the same way this CHR this cell secondary gamet it has how many chromosome 23 but double structure right so it is also how much now one small n 23 chromosomes double structured and hlid number of chromosom but amount of DNA is double is it right
42:08 because every chromosome is double structured is that right so what we'll call it it is 2N DNA right 23 double structured 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 n right or it is called haid is it right applied but when you talk about amount of DNA it is 2 N why it is 2N even though chromosomes are 23 you may think it may be 1 n but because every chromosome is double structured so double amount of DNA so it's 2 N is that right now here I want you to be very
42:55 clear when the beginning of the meosis primary gamet are at the beginning of the meosis and one primary gamet gives secondary gamet at the end of first miotic divion at the end of first metic in the beginning how many chromosomes were there 46 46 double structured so they were di cells with 4 n here are 23 but double structure so H number of chromosome but 2 N is it right so this complete our first metic division after the first miotic division these cells do second miotic division but when they enter and directly enter into second miotic division without replicating their DNA further so these 23 chromosomes which are double structured at next stage just their
43:42 centrom disjunction what breaks down splitting of the centrom and when the centrom break down each Chromo go to other side this was double structured chromosome and out of every double structured chromosome one structure go to one side and other structure go to the other do cell right so it means double structured chromosomes or chromosome with two chromatid split at the centromere point and here centromere break down right here only homologous chromosome were going away during meosis 1 and meosis 2 croos will break down and double structured chromosome one double structured chromosome will convert into two single struction chromosomes which go to the opposite pole and go to the daughter cell now how many single
44:28 structured chromos double structured chromosome were here 23 double structured they will eventually break down into 23 46 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 Hite cells right but double structured they will again break down in the centromere and single structured chromosome will go to the ends now these are the final product of second miotic divion right at the end of the second miotic division right we were having at the sorry in the beginning of second miotic division we were having how many secondary gamet two secondary gamet and how much M final cells are
45:14 produced four cells right now in this case these four daughter cells which are produced at the end of the second miotic division every cell has how many chromosomes 23 chromosom so every cell has 23 single structured 23 chromosomes which are single structured right so it should be one small n or we can say this is this number is haid what is it holid but if you talk about amount of DNA here what how how much is that 1 n is that right so all these four cells which are produced as a result of the second miotic divan all these four cells will have hlid number of
46:00 chromosome every chromosome is single structured but every chromosome may be slightly different from other chromosome due to crossover and random assortment and amount of DNA is one n is that right now advantage of this is by the end of the miotic divion first and second every germ cell sperm or ovam is having applied number of chromosome so my sperm will provide hlid number of chromosomes and my wife om will also bring hlid number of chromosomes and when they will fused together in the zygote after fertilization zygote formation will be reestablishment of diploid number of chromosome am I clear any question here
46:46 you mind drawing that for a female yeah what is that at this stage what happens to female ogenesis or spermatogenesis let me explain in super Genesis what happens that one primary in superat Genesis one primary gamet which is primary super site divides at the end of first Meo division into two secondary supery and then each secondary supery divide into two spermed which eventually mature into two sperms so because two sperm will come from this secondary gamet uh supery and two will come from this so in m from one primary gamet how many secondary gamet are made four all of
47:33 them become mature Spa but in female there's a little difference the difference is that one primary gamut during first myotic division when it makes two cells one cell will get all the cytoplasm and this cell is called secondary oite other cell will get very little cytoplasm and that is called first polar body then in female when secondary gamit is going to be mature ovam then P secondary oite secondary oite divide into two cell one cell takes all the cytoplasm so this cell with 23 single structured chromosome and all the cytoplasm this is
48:20 called definitive ovom or mature om and other is called second polar body is it right which is the second daughter cell uh which is getting almost no cytoplasm meanwhile this first polar body also divide into two cells and they're also called third or fourth polar body so we can say that actually what happens in female out of the four what is this four final daughter cells one become definitive o and three are polar bodies and the difference in polar body and definitive oom is definitive o gets all almost all the cytoplasm polar body get very little cytoplasm and they degenerate is it
49:06 right they are not functionally useful right now if someone ask you what is the purpose of meosis meosis is a very specialized type of cell divion which occur in the germ cell to make the mature germinative cells and males they make sperms and the females they make OA is that right during mosis has two stages first stage and second stage of meosis is that right now during meosis some during first step of meis some special events occur number one homologous chromosomes pair with each other synapsis then homologous chromosomes cross over and exchange genetic material and then they're separating from each other and making structure of gasma and eventually they align themselves and they separate from
49:53 each other but remember the croos don't break down this is first myotic division in the beginning of the first myotic division we have which cells primary gametes at the end of the first biotic divion we have secondary gamut primary gamuts are 46 chromosomes double structure four and DNA material secondary have each have 23 23 chromosomes and which are also double structured and two n genetic material in each daughter cell is it right then when these secondary gamit go to the second biotic divion simply these cells don't go into interface because in interface DNA replication should occur but they do not go into interface cells from second first miotic division directly go into
50:38 second miotic division without replicating their DNA but what they do double structured chromosome break apart at center right centrar and uh single structures or single chromatid go to the daughter cells each single chromati from the double structured chromosome go to the cell and two secondary gam eventually make four final daughter cells any question you have diversity diversity genetic diversity is assured during these steps number one genetic diversity occur for the Next Generation number one due to crossing over where genetic blocks of genes are exchanged number two genetic diversity is further ured the random assortment of maternal
51:24 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 sperm and genetic material from the OV fused with each other they're having different combination and an individual come with unique genetic makeup any question here there's no question let's have a break
