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 chromosomes 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 centro meres right now in this early cell before it enter into meiosis one right this early cell so for metagonia the number of chromosome is 46 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 say 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 three from father paternal then it must be chromosome number three 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 homologous to each other mean chromosome one of mother is homologous to the chromosome one of the father chromosome number ten coming from mother should be homologous to the chromosome number ten of the father is that 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 chromosome is that right now in this case the both chromosomes are having the 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 the terminal side then on this homologous chromosome coming from particular 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 is a gene which determines structure and function of a specific enzyme right then on the corresponding 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 a homologous chromosome at the same loci right these genes are in specific 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 alleles of each other what are they they are alleles of each other and what is this gene for the supposed size of the nose the shape of the nose from father side this is the gene for the shape and size of nose from other side so these two genes are also alleles of each other then if this was a gene from paternal side for a specific enzyme and here on the same locus in the homologous chromosome coming from the mother side also has the same similar gene for the same enzyme then these genes are also alleles of each other so what we can say when two chromosomes are coming from mother and father is that right and they are having similar genetic material such chromosomes are homologous of each other and on 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 is that right any question after this no problem now you must remember also one more thing these are the chromosome letters suppose chromosomes are three paternal this is called single structured chromosome right this is also maternal chromosome but this is also single structured when chromosomes replicate their dna chromosomes become duplicated let's suppose this chromosome right it replicates 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 in duplicated chromosomes right of course dna material is double is that right because dna 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 chromosomal number is basically counted on the base of centro here 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 is unreplicated dna double structured chromosome as replicated dna is that right single structured chromosome is also called 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 that right but if this situation is there the 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 with 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 that right homologous chromosomes have homologous alleles 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 body super metagenesis is going on and if super metallogenesis is 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 would mean myotic division which is a specialized type of deviant which occurs specially in formation of germ cells and gametogenesis is that right now let's suppose this is in my test is this is the primary cell of course my testes will not have ogonia right hopefully now we come to super metagonia b now super metabonia b in my body it has 23 [Music] and then let me write here it has 23 maternal chromosomes 23 methyl 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 one small n so we will choose a term here that in this cell so metagonia there is number of chromosome one small n from which side patternal 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 too small n and when they're too 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 chromosome is too small n or 46 we say it is diploid number of chromosome what we call it yes diploid number of lloyd number of chromosomes i'm talking about this cell which is about to enter into meiosis one now another thing this was about the number of chromosomes 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 and what is this this is also single structure 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 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 chromosomes now if we talk about there are 23 paternal chromosomes single structured what we will say that there are one n paternal chromosome and one n mean 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 1 capital n now when i say it is one small n situation it means there are 23 paternal chromosomes and if i say 1 capital n it means it is single all 23 chromosomes are single structured what is this single chromatid or single structured all 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 a terminal side there again one end from eternal side so 23 chromosomes set from eternal side and each chromosome is double structured single structured here single structure so it will be 1 n single structured is that right so in this case what we will say that 2 1 small n plus 1 small n so what is the number of chromosomes 2 small n or we can say what is the number of chromosomes total 46 so this cell has 46 total number of chromosomes and diploid cell but look at the dna of it it has 20 23 23 single structured from paternal side it has 23 single structure chromosome from maternal side so one n from a terminal side this is amount of dna so amount of dna from mother is 1n amount of dna from father is 1 n so how many capital n amount of dna 2n is that right any question up to this no now we come to this situation actually what happened before the cell is entering into meiosis one if before the 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 when all the dna is replicated all the chromosomes will become double structured chromosome what they will become double structured chromosomes it means when these single chromosomes will become double structured chromosome here so these structure will convert into this type so it means every chromosome with a double structure now this cell double structured chromosomes right this is called yes what is this called 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 super metacite is that right now in the primary super meta site which is derived from super metagonia b or in the female primary oocyte which are derived from ogonia right they are having double structured chromosome because they have already replicated their dna and if they have already replicated their dna now very carefully will talk about this structure right how many chromosome paternal chromosomes are there now we have 23 paternal chromosome but double structured here were 23 paternal chromosomes with single structure so what will say that paternal chromosomes are 23 how many petroleum chromosomes are paternal chromosomes are 23 and how many n one n one small n is that right and plus on paternal thigh maternal side yes maternal or how many look at this cell there were 23 single structured and here there are 23 double structured so we'll again write 23 but double structured maternal chromosomes is that right and how many small energies there it is still one small end because even though they are double structured but actually the number of chromosomes depends on number of centromeres is that right so how much it will make both of them together total chromosome will become small two and small or we can say total number of chromosome will be yes no it will be still diploid the cell in the beginning will be still diploid but there's a 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 structured now if you are talking about the amount of dna now here the amount of dna was 2n 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 1n has become 2n so 2n in paternal set of 23 chromosomes so we can say that paternal this is actually 2 capital n amount of dna here it is how much again 2n because it is also double structured so total n will be how much 4n so we can say that primary gametes primary gametes mean in males primaries of metal sides and in females primary oocyte 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 that right any question here