Cell Cycle and Genes - Mitosis & Meiosis

right so today we are going to talk about cell cycle some detail about mitosis and certain genes which are regulate the different steps during the cell cycle right and what is the role of such genes in development of cancer so let's start with a very simple concept there what is self hi color right cell cycle basically a concept related with that how a cell passes through different phases to divide into two daughter cells right what is cell cycle cell cycle is consisting of all those events and phases through which a cell passes a mature cell passes eventually to divide into two cell right now let's start there normally cell cycle has two parts number one is called interphase and second is called mitosis so let's go with the examples let's pause then the cell cell here right and this cell plans to divide right this is a mature cell here and it gets stimulus and it's going to divide of course when cell is going to divide it has to duplicate its genetic material there's going to pass through the mitotic division so it has to duplicate a genetic material as well as it has to increase its what cytoplasm proteins and organelle is now when this cell is planning to go for Debian now first of all it has to duplicate its DNA is that right so let's pause cell in this stage it is duplicating its DNA and I put DNA molecule which is open and it is being replicated it is being replicated over here DNA molecule now when cell plan to undergo the vien it does not directly start replicating its DNA before starting the replicating its DNA cell has to produce lot of proteins a lot of enzymes right increase its cytoplasm increases organelle is and produce those enzymes right which can help in the replication of DNA and produce all those proteins which should help in replication of DNA so this stage where DNA's been synthesized we call it s straight as phases phase of DNA synthesis and phase of cell before the DNA synthesis right that is called pre synthetic phase what is this phase pre synthetic fail synthetic mean synthesis of DNA now this phase which is pre synthetic phase right this is also called get one or growth phase one or simply we call it g1 is that right so when a cell plan to divide first it will enter into g1 phase where it will do all its preparations at molecular level and organelle in ever to synthesize to get ready to synthesize the DNA then DNA synthesis process will start right so all during that time when DNA synthesis is going we call this phase as phase and once the DNA has been synthesized mean DNA has been semiconservative like replicated when DNA has been replicated right it means that 2n has become foreign right all we can say when DNA is replicated every chromosome has become double structure chromosome right after that was DNA replication is complete now it has to go to next phase in the next phase it should get ready it should get ready to divide that genetic material which has been duplicated for the two daughter cells now the cell is preparing proper synthesis when cell is preparing itself to divide the nuclear genetic material equally into two daughter nuclei right that preparation phase is called g2 or growth phase two or gap 2 so what is g2 g2 is post synthetic but pre mitotic phase post synthetic but pre mitotic phase during g2 phase what's going on cell is getting ready to divide it duplicated DNA into two daughter nuclei is that right now once it has been through the g2 phase eventually it will enter into next faith where it is going to divide the genetic material and this nuclear membrane will eventually dissolve in genetic material will go to both sides of cell so that it can go for the new two daughter nuclei now that phase in which nuclear duplicate it or replicated DNA or chromosomes they are under the process of the V n is the right for the two daughter nuclei this stage is called mitotic stage what is it mitosis stage or simply call it M phase right now after the M phase eventually when cell has divided into two cells right it has divided into two cell in some cases then some tissue cell directly enter into next cell division and some other tissues cell may go and take rest right and if cell goes out of the replicating cycle of proliferative cycle we say it has gone to growth phase which is g0 is that right so let me repeat it rapidly rather why don't you repeat for me yes cell cycle comes what is cell cycle cell cycle means all the events which are occurring in a cell when it is going to divide from one cell into two cell to divide one cell into two cell we have to basically May cytoplasm or organelle is more and specialy DNA should be replicated and equally divided into two daughter cells now first g1 phase what is that cell is getting ready for synthesis of DNA it is getting ready for synthesis of DNA it is not yet dividing its DNA right so it is pre synthetic phase is that right then DNA replication started sentences start right s phase then cell enter into the preparation that how replicated DNA should be divided for two cells for example here it will make the proteins which are related with yes spindle formation once those proteins which are required for the vien of cell they are made then cell will start separating its chromatids a replicated DNA and go through processes which will make two daughter nuclei eventually two daughter cells that is mitosis right and as soon as it ends up mitosis end up in some tissues cell may go again into proliferation and in other tissues cell may exit out of the cycle and start resting and they may come into cycle again if there is appropriate stimulus for proliferation right now those tissues in which cell the cycling continuously there are some tissues in our body that cells there are continues continuously multiplying it means as soon as cell completes its mitosis it entered into g1 cell it does not go to G 0 and G 1 and again process start can you tell me some tissues like that yes please yes please skin very good skin cells right there all that I am multiplying any other tissue gastrointestinal gastrointestinal cells they are all the time multiplying is that right so such cells or tissues are called that in these tissues we are seldom deploying all the time seldom multiplying all the time we call those tissues the cells there are labile cells the violet cells are those cells which are multiplying all the time in the tissues and these cells once they complete mitosis the don't enter in G not once they complete one Dominion they go for the next two via is that right they are labile cells such cells are seen in classically in your gastrointestinal system such cells are also seen in the skin some of the skin cells are continuously replicating they don't go into G naught phase and then such cells are also present in bone marrow hematopoietic cells metabiotic cells also keep on multiplying after the labile cells then there are some other tissues in which once seldom completed a cycle if that tissue does not require more cell cells will go into G 0 state and cells will remain in g0 stage where they are doing housekeeping function the genes which are concerned with the housekeeping of the cell only those genes are working plus if that tissue has some special function those genes are working but cell is not planning to divide so in some tissues cells come out of the cycle going to g0 but the appropriate stimulus they can be forced to read product again right such tissues are said to be stable tissue stable tissues mean that are stable cell and some issues there are stable cells stable cells are those cells when in the tissue most of the cells are in which phase g0 but normally they are not regularly multiplying but if there is appropriate stimulus they can multiply is it right so can you tell the example of stable tissue yes please not neuronal cells not muscle cells you are going to miss your and see - yes stable tissues we have cells are normally not replicating but if there is appropriate stimulus cell can leave the g1 stage and enter into the rapido none of you knows it Wow why don't you tell me liver a better science a better side some normally not multiplying in a very fast rate most of the hepatocyte most of the time are in G naught but if you cut a piece of liver then cells will come out of G naught they will enter into cycle g1 and then they will start multiplying and make it good just the right cells in the kidney ubios nephron cells cells in the pancreas so these have which are not in these cells in these tissues there are stable cells what are stable cell population with most of the cells are arrested in G naught and there just means the general and special functions but not planning to multiply but if there is a property of stimulus they can be brought into cycle and multiply clear then there are some tissues they are cell their permanent sounds permanent cells mean permanent cells mean that in those tissues once cell them divided they're going to G not phase but they cannot re-enter into g1 in some tissues some cells or most of the cells once they have multiplied and gone into g0 phase right you cannot bring them back into cycle so those two shows cell the permanent and they don't multiply if you want to increase the cells in those tissue then you have to find the stem cells in those tissues we should multiply but in these tissues where there are permanent cells one for permanent cells are very differentiated they are doing their general and specific function they cannot be pulled back into cycle yes what are these tissues what are these cells now you can tell me in your own our cells neurons they are permanent is the right you cannot drag the neurons back into multiplication or proliferation cycle then there are muscle cells don't tell me just muscle cells booth muscles can proliferate tell me a little muscle cells and myocardial cell right so skeletal muscle cells and myocardial cells they are permanent cells that once they are fully differentiated you cannot they will go into g0 phase and you cannot drag drag them back over here am i clear any problem up to this now one thing which is very important to understand first of all I will go briefly into stages of mitosis how do you define mitosis yes mitosis the VN she thinks the vienna fellows mitosis anyone will come with better definition what does mitosis let me tell you don't confuse first you should be clear what is in cell cycle what is mitosis and what is interface interfaces G one g1 phase plus what is this S phase and plus g2 phase it means when cell is prolonging and making lot of proteins so that it can enter into DNA synthesis plus when cell is self replicating its DNA and plus when cell is making protein than organelle ready for mitosis we say all these stages from here g1 s up to g2 all these stages right they are together PI interface what are they called interphase but this stage is called mitosis now I want that you should be very clear whatever mitosis yes okay he is telling us somatic cells when they divide the divide by mitosis you are right and germ cell when they divide eventually they go through me or take the VM I'm asking what is mitosis yes please this is about the division of nuclear material listen carefully when I say there is mitosis going on what does it mean that is at this stage during the process of mitosis right the replicated or duplicated genetic material in one nucleus should be divided for two daughter nuclei so when you are talking about mitosis we are specifically yes focusing on the Vienna nuclear material is that right that cell during the synthesis has duplicated this genetic material and when cells start the process of dividing the duplicated genetic material a replicated genetic material into two sets of identical genetic material for two daughter cells that is mitosis and the process in which cytoplasm and organelles is also divided into two and cell membrane separated into two that cytoplasmic and it's organelle is division into two cell is called cytokinesis so you should be clear about mitosis and cytokinesis what is mitosis mitosis is that once synthesis of DNA has been done once DNA has been replicated after that when it is going to duplicated DNA are duplicated genetic material of the nucleus is going to under process so that it can divide the nuclear material duplicated for the daughter cells this is mitosis and during this process mitosis is going for the nuclear materials but during the mitosis also organelle is and cytoplasm and cell membranes are undergoing the vien so that not only there are two nuclei but there are two daughter cells and this process of dividing the cell into two daughter cell is cytoplasm of the cell band - you call it Saito kindnesses this is that right any problems here no now very briefly what are the stages of mitosis I know all of you know it very well the start teaching from high school in the keep on teaching doctors until they are there so stages of mitosis before I go into really detail attention please again never ever in your life mix the mitosis with the interphase interfaces when cell is planning to divide getting ready for Debian is there right that include g1 pre synthetic phase synthetic fail pre mitotic phase right this is all interface and this is I'm going to explain stresses off mitosis in which mainly we are focusing on what nuclear material to be on is that right now this nuclear division during the mitosis there are four phases of mitosis what are those four phases of mitosis who's going to tell me four phases of mitosis I know everyone knows that very much yes yes she knows it's prophase very good then then it will go into what prophase into metaphase and then okay let me put it profiles here prophase goes into yes metaphase and metaphase goes into anaphase and nfl's goes into t low phase is the right how do you remember that you remember them about you remember that but on him there's easy way to remember that just pee and mate right P prophase metaphase anaphase telophase is there right okay don't stimulate your imagination too much concentrate on the lecture now what happens in the profiles listen this profiles which I'm drawing here actually if I say that this is g2 and mitosis is going from here up to here is there right now when cell is going through this phase what are the changes coming of course you know that changes are prophase yes metaphase anaphase and telophase but this is not enough to know what happens during prophase let me make a cell here right and we are going to see what happens in their cell during the profiles now just before the prophase cell was going through g2 during g2 what has happened this is a nucleus nuclear membrane at this phase I'm talking about before just prophase right there is what g2 phase there is well clear-cut what is this nuclear membrane that DNA is prominent of not during g2 chromosome the well prominent or not once that D you know normally when DNA replicates itself it opens up right and it condenses during the profiles so originally in the beginning of before the probe before the prophase DNA is very light okay let me give you some different color for DNA DNA is double structured but genetic material across they are making lose network this is before the profiles and centrioles may be randomly present over there now now this cell which is in g2 what is the cell isn't g2 now it is about to enter are entering into prophase when it is entering into prophase I told you it is phase of mitosis and mitosis means separation of genetic material of nucleus into two identical set so what should happen logically tell me what should be the next step in the cell what should be the next step first to follow before you do anything these these loose chromatin condensed itself what should happen this loose chromatin condenses itself when loose chromatin will condense itself then what will happen that chromosomes can be seen more clearly because they become condensed and every groups will be single structure or double structure it will be double structure because during synthesis phase we replicated the DNA so now here where chromatin is moves it becomes condensed chromatin and you are able to see the chromosomes double structure is there right so what is the first step in prophase chromatin become condensed and what is becoming more visible chromosomes which are visible as double structure plus do you think if nuclear membrane remain impact can you divide this into two daughter nuclei no it's the next step is that nuclear membrane start dissolving nuclear membrane starts dissolving and with that we are going to make spindle and to make a proper spindle we have to get the centrioles at the what is this at the edges two opposite pole so these are the three basic changes which occur in during prophase that chromatin become condensed number one number two nuclear membrane become indistinct and start dissolving and disappearing because there are special nuclear proteins here which are called laminin and some enzymes will come and they will phosphorylate the lemon in proteins and then lemon in protein becomes phosphorylated nuclear membranes start dissolving in the same way in the chromosome there are proteins called histones his stone one when histone one get phosphorylated the nucleus star these chromosomes start getting condensed this is a right so phosphorylation of his taunton what is this chromatin condenses this phosphorylation of lemon in in the nuclear membrane dissolve this an arrangement of centrioles at the polar end this is prophase as some earth now listen carefully as far as this membrane totally disappear and microtubule start developing clearly cell will go into next phase next pose this is here the nuclear membrane has disappeared century all the present over here this is one central this is other central and you've you start extending right micro why this spindle is being made because this double structured chromosomes should be really doing that structure before that the beer is that right so that there should not be mistake during the division of genetic material so next phase is nuclear membrane has been disappeared and microtubules form mitotic spindle is formed and your genetic material which now consists of what chromosome which are double structured they are arraigned on equatorial plane right and then mitotic spindle is very clearly formed and dense chromosomes are arraigned on the spindle and especially these what is this tubular microtubule get attached what is this point and you talk course the point where two chromatids what are promoted when one chromosome has doubled structure each structure is called chromatid both structures are identical chromatids look this is single structure chromosome and after the S phase every chromosome become double structured and this double structured chromosome has two identical right material each material is called chromatid one and chromatid two now if each chromosome consists of two chromatid because each chromatid will go to one daughter cell and plus this is a special point where the tubular will bind microtubule mitotic system will bind here and here what is this chi neato curved Chi need though I don't know you call it true or cool it's up to you this is it right now once cell is at this stage this is called metaphase prophase has gone to metaphase how the prophase enter into metaphase but losing its nuclear membrane condensing it's yes chromosomes are engineers micro tubule formation system ascentria and when central up tubules and chromatids are double structure chromosomes are arrayed on these spindle we say cell is in which phase matter faith once this has been done cell will go to the next stage next stage we are dividing the nuclear material into two now long what has happened each double structured chromosome look here each double structure chromosome will break at this point right and then this tube you'll this will pull this part to one side and this part of the tube might a spindle will pull the other chromatid to other side in this way from every devil structured chromosome which will break at its centromere and each chromatid to start moving to the opposite pole is that right so at that very phase when this is going on right this double structure have been broken and now it is been bred to that side and other structure which are counterpart with that that has been brand on other side same is true over here so what has happened that these double structure of chromosomes having two chromatid is actually broken in the centre is the right and two identical chromatids are moving to the opposite Pole when cell when you can see structure like this we say it as go on into anaphase and eventually it will come to which stage Pirlo phasing Tilo phase what happened yes until of phase now this cell will start dividing it's what is this even cytoplasm right so the cell will go into this phase now it is playing two daughter cells and these chromatids have reached right to the pole here and here here and here now what is the next thing to be done you will now yes you will now bring the membrane bad right so what is that thing going to happen there in this phase which is still a phase you we are making the nuclear membrane right so actually original nucleus which was that the prophase is now appearing as yes what - daughter nuclei right and with that now during this phase again it will lose its condensation and chromatin will become loose originally chromatin was loose in the end again it will become loose originally nuclear membrane was there in the end nuclear membrane will again form right and when this membrane cell membrane is coming from the side and about to divide into two so that cytoplasm an organelle is also divided into two we say cytokinesis is going on so in the tillow phase what happens chromatid from double structure has been separated and reached to the pole nuclear membrane again appear and cytokinesis is completing and cell divided into two any question up to this there is no question okay so this was very basic information now we go to little more detail listen carefully we have not discussed what forced this cell right we have not discussed what forced this cell to move from G not up to g1 and go to synthesis phase and then go into g2 and mitosis phase did we discuss those factors no we just said that there was one cell in G not it started preparation for the DNA synthesis and that is g1 then is started DNA synthesis as phase then let's started preparation for mitotic or nuclear division g2 then it went under nuclear division that was mitosis emmaclaire but actually we did not talk about who told this cell that let's start the VM because sell the VN is very very regulated phenomenon very very regulated phenomenon if cells start proliferating out of control do you think you will remain so beautiful suddenly this here become like that nose goes like that all the cells to be n is very very regulated question is that that a simple part that these are the interface and this is mitosis and cell one shall become two self does not know much medical advance now you are studying medicine in a times where now we really know how this cell decides to enter into division what are the molecular signal to a cell that it is entering into g1 phase we know what a molecular level what is going on into this cell does that right not I will tell you something very interesting you know here that DNA replication will start right do you think if the cell which is going from G 1 up to s fair if already its genetic material has been damaged by radiation or by a virus or by some chemical substance right give a cell sitting here it has entered into g1 phase it is planning and getting ready to duplicate its DNA but let's suppose this DNA's are already injured or damaged do you think the cells should be allowed to go from g1 phase to DNA synthesis without repairing its DNA No so what happens at this point at this point where g1 phase is about to enter into as far as fair there should be special event the special activity here what is this activity before the cell enter into starting its replication all its DNA should be scanned and made sure that its DNA healthy and if there are some mutations or there are some DNA damages they should be repaired only then after making this surety cells should be allowed to move from g1 2 s is it good for us or bad for us very good for us that every time cell is going to proliferate during the g1 it is ensured that this genetic material is absolutely correct only then it can enter into S phase so there are some special we said normally there's a hurdle here there is a hurdle here there is a problem here that one cell is rapidly coming to this phase of the cycle if it does not ensure its DNA is not okay cell will be arrested at this stage cell will be if DNA is not okay cell will be arrested at the stage and if it is confirm if DNA is okay right then cell will be allowed to move forward this point we call it checkpoint you know when you are moving from one country to other country there's a checkpoint where they check your passport and everything here cell is going to check what originality of its DNA right we call it a checkpoint what is this checkpoint this checkpoint is the point where if DNA is not okay cell can be arrested at this stage repaired its DNA only after that it can pass through this checkpoint this checkpoint is called g1 checkpoint g1 checkpoint or we call it g1/s checkpoint is the right once it is ensured that DNA is having no dangerous mutations or changes then whatever DNA is here it will replicate once the DNA has been replicated it will enter into g2 phase getting ready for one it's getting ready for what dividing this replicated DNN - to sell another checkpoint will come here you know what our enzymes are going to do at this state now they are going to scan all that the NL make it sure that all during the replication there was no error do you get it or not it is just like that that if you are going to make photocopy of a book first you make it sure at first checkpoint you making sure all pages are okay then you make the photocopy there two copies then again in sure before you give these two copies to two persons you ensure there's no mistake in the copies do you understand it this is second checkpoint what is this checkpoint card g2m checkpoint at the end of the g2 and before the mitotic state this is second checkpoint and here again it will be checked that every chromosome is really what is that duplicated yet suppose one chromosome is not duplicated properly Ramos for number ten is not duplicated but all other chromosomes are duplicated there is no way a cell can move forward until it does not complete the replication of the missing part of the DNA you are understanding me so this is second checkpoint if it does it at this point also it is also chip now it is moving forward right some people believe there is another checkpoint where it is made it sure that all the DNA is properly aligned on mitosis so that before the final in division we should know it there's no mistake that is called em checkpoint and mean checkpoint during the mitosis but at your level you should be very good the concept of - checkpoint number one g1 checkpoint do you want to s right and second is yes g2 - and in both itself cell can be either arrested here cell cycle at first checkpoint or at the second checkpoint why it will be arrested if there is DNA damage before the replication it should be corrected or DNA is damaged during the replication again it should be corrected before mitosis start now you must be thinking what are exactly these checkpoints right again many of our cells right now many cells in your body are either in G not they're resting or they are in g1 many cells spend long time during g1 and they cannot multiply if they don't come over this hurdle now how it happens right I'm going to take this cell out and make a big diagram here right which cell not all of them I'm going to just take this cell as an example make it a big diagram here and now I will tell you at molecular level how this cell knows now it is trying to multiply is there right and what are the molecular events which are occurring into the cell so that cell can pass through the g1 phase and how cell will jump from the checkpoint and eventually enter into S phase now we are going to target molecular level now we are going to see how the cell cycle progression is controlled remember if g1 at the end of the g1 everything goes okay only then shall will enter into as phase and during the S phase if everything goes okay only then cell will enter into g2 phase and at the end of the g2 phase is everything is okay only then cell will enter into mitosis phase now we have to see that what really happens inside the cell let me make one big fail here now this you should draw now this cell is in g1 phase it means it is having all the good intention of proliferating right now let us suppose this is genetic material in the cell you know every gene either double copy one copy is coming from mother and other copies coming from father was the right every gene has two copies two alleles now I'm showing here suppose mental maternal chromosome material from chromatin and here paternal and on this line I will arrange that different genes which are important during replication when a cell is about to replicate what happens right first a basic principle let us suppose here are the genes just suppose that here are the genes of course this is maternal this is paternal so here are the genes that once these genes are activated cell will start replicating its DNA if we activate activate this point cell will start replicating its DNA it means if we activate this gene set what will happen cell will jump from g1 to S phase you are understanding car will start now there are some group of genes here look here the some group of genes here let me make it more clearly first of all if you imagine that there are some genes over here the group of genes when these genes are expressing the force this system to force the cell to multiply they are having a positive effect on these genes and there's another set of genes here if these genes are stimulated with a whole set of genes here and if this genes are stimulated then hibbott the cell replication what does it mean that look this is the genes once they are activated they'll start duplicating its DNA is there right now these genes these red genes if they are expressing their product will lead to cell DNA synthesis or applet DNA replication if these are working well what will happen DNA replication will not occur right it means that when cell is in g0 phase or g1 phase it is not replicating its DNA is that right and cell is in g1 phase of g0 phase it is not replicating its DNA it means in that situation these genes are under working and these are over working and keeping the cell arrested before the S phase this is that right but if these genes start over working and these under working cells will start replicating its DNA and jump from g1 to S phase is that right no problem we can also say that is cell is like a car and you are going to drive the proliferation process these are accelerator genes and these are biological brakes is that right when these genes are expressed cell accelerates into proliferative phenomenon and jumps on what g1 2 as phase from first checkpoint but if neither dominate dominating liver working cell will be arrested you have plied powerful molecular break and they cannot sell cannot jump into s-phase Claire the question is what are these set of jeans is it clean of course they are not accelerator the way they are in your car what are these jeans exactly let me explain now I will go into detail off what are these jeans right and later on I'm going to detail off what are these jeans right let me tell you this is first Jean of course there should be another copy here also but I will not go along now onward make only one copy this is the Jean whenever is this Jean expresses itself what will happen yes whenever this Jean will express it will make of course messenger RNA and proteins but it cell throws these proteins out these proteins come out now this Jean is producing some proteins and they are secreted out of cell cell is planning to the placate then the next field next gene express yourself next Jean expresses itself and its product gets inserted where inside the membrane is that right now what is happening the first group of gene has produced a product which has been secreted by the cell and second group of gene hasn't produced a peptide product which is inserted into membrane then what happen this product comes and work on it here what is this this is actually a growth factor and this was the gene for growth factor so first of all genes forego growth factor are stimulated and they start producing the growth factors and then second a set of genes is also expressing and they are expressing the receptor for growth factor am i right what is this receptor for growth factor now selleth produced the growth factor which is acting on the same cell which is also expressing the receptors for growth factor does that right then third gene will express here what this gene will do it will produce a product and this product will interact from here right and it will give signal back to the nucleus it means these who are going in direction now you are going to tell me just four little repetition first gene was producing what growth factors or mitogens other name for this is my toe germs my Trojans are North Katrina soluble nitrogen's right and cell growth depends on the presence of soluble nitrogen's plus cell proliferation also depends on their cells should be anchored with each other I will talk that later second is second gene is concerned with what what is this growth factor receptor as the right third gene have expressed itself and it is produced a protein and what is this protein what is this protein signal transducer protein it will take the signal from the receptor and throw the signal back to the nucleus so what is this signal transducer trance do you sir protein am i right cell is getting ready to multiply all these things are happening during the g1 phase their cell is under the influence of growth factor cell the receptors of growth factors are activated though receptor activate that signal transducer proteins and signal transducers mechanisms are giving signal back to the nucleus this is a right in the nucleus these incoming next gene is activated right now next gene when this gene is activated what this gene is going to do it is going to produce special type of transcriptional factors right the next gene has produced type of proteins which are in the nucleus now is a transcription factor is that right now when once this gene set is activated these are called responder genes what are these genes again this was growth factor genes is the growth factor receptor gene what was this signal transducer genes what are these responder genes responder genes which actually respond to the signal for the growth and they produce transcription factor right these transcriptional factors will act on special kind of gene here is the right they will act on this special type of gene and this gene will express itself right and produce special type of molecules and these special type of molecules are called what is this cycle cycling's what are these molecules Cyclones is that right now as soon as cycling's are produced there is someone who like to go on cycle who's that there's another gene here right there's another gene here and this can produce special enzymes and this gene expressed all the time remember this gene is a very special gene what is special gene in this this gene not cycling other gene this is active all the time but cycling genes are activated only when cell is undergoing replication cycle or cell proliferation cycle cycling genes will only Express when the mitogens of growth factors are there when their receptors are there when signal transducers are there when responder genes are producing transcription factor only then cycling produced but these protein this is being produced all the time now as soon as cyclin is produced this product of this gene will interact with the cycle now let me tell you what is the name of this protein now this protein actually does the phosphorylation of target molecules what is this protein doing phosphorylation of specific target molecules but this will only work when it is riding on the cycle it means this protein is the kinase kinase mean it can phosphorylate target proteins but this kind is only worth when cycling is there so we call it cyclin dependent kinase is what we call this cyclin dependent kinase is the point which you have to remember is that in the cell cyclin dependent kinase is the present all the time but they are not active cyclin dependent kinase is only become active when their relative relevant cycling's are produced but cycling's are produced in cycle different cycling's are produced as in the proliferating cell at a specific cycle is there right now let's come over here that as soon as cycle has come cyclin dependent kinase is already there so what will happen they will interact with each other they will interact with each other both of them and now what is this here cyclin having a combination of what with that cyclin-dependent yes kinase now cyclin-dependent kinase is active or inactive it is active when it is active now it will start doing its phosphorylation function is that right don't forget our whole target was what to activate these genes but I have started story from other end now one cyclin dependent kinase is are loaded with the psyche waves they become unsigned matically active and what they do I will tell you in the cell nucleus does our dog here I don't know how to make a dog okay I will do some effort okay this is less like a dog but you just believe it is a dog right this is our dog and the nucleus the other dog and this is a doggie is holding yes special type of what is this transcription factor until this transcription factors in the mouth of the dog these factors cannot activate these genes but if this utk you remember cycle independent cdk this complex whatever this cycle independent GDK with the cyclin right this complex can do some naughty thing to the dog you know what they can do it what they have done dog has open its mouth and very uncomfortable and what has happened here this key has gone out and started working here actually what is done by cyclin-dependent kinase is when runs their activity to the cyclin basically they phosphorylate this dog when this dog is phosphorylated it's just like offering too much bone to the dog and it will lose the key right as soon as you lose the key it will go and start what this thing this set of genes this set of genes are basically the genes once these are activated cell will start producing the product which will ensure the onset of DNA replication and now cell will jump jump from g1 phase to S phase right g1 phase 2's phase am i clear right let's have a break and then we'll continue

Channel: Dr. Najeeb Lectures

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Keywords: cell, mitosis, meiosis, genetics, dr najeeb, dr najeeb lectures, medical lectures, medical education, usmle, usmle step 1, biology, mitosis cell division, cell division, cell cycle, phases of mitosis, interphase, anaphase, telophase, prophase, spindles, steps of mitosis, chromosomes, mitosis vs meiosis, cell multiplication, amoeba sisters, cytokinesis, cell membrane, cells, cell biology, dna replication, sister chromatids, dna, genes, dna duplication, centrioles, dna replication animation

Id: Ev1rGysfTZY

Length: 55min 31sec (3331 seconds)

Published: Mon May 27 2019