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Current time:0:00Total duration:10:09

Video transcript

so we talked a bit about the different types of cells in the blood and how all of those cells are actually made inside the bone marrow so inside this cavity in the centre of bone and surprisingly all of these very very different cells actually come from they originate from one cell and that's the cell that I'm drawing in over here and as we talked about before this cell is called a hematopoietic so I'm at O poetic stem cell and this hematopoietic stem cell is responsible for creating all of the different cells in the blood so instead of talking about it I'm just going to draw that I'm going to draw this hematopoietic stem cell creating a blood cell and this could be any type of blood cell but we know that since the cell was just made it was just created it's an immature cell this is an immature blood cell and we have a name for it mature blood cells we call them blast cells so this is an immature blast cell and in these immature blast cells are really big cells and they have these really large nuclei so as you can see the nucleus takes up pretty much the entire cell and the DNA inside the nucleus is usually really loose and disorganized and kind of all over the place like I'm drawing it in over here but this cell doesn't stay immature forever eventually it moves along and it starts to mature and as the cell matures it gets smaller so that's really important it gets smaller and the nucleus inside the cell also gets smaller and you guys are probably saying well obviously as the cell gets smaller the nucleus inside it also has to get smaller but this is more than that in this case the nucleus is actually taking up a smaller percentage of the cell so it's taking up less room inside the cell and and even the DNA inside the nucleus changes in appearance it becomes a little bit more organized a little bit more like that and then this cell continues to mature and and it passes through a couple more stages until it reaches its final stage and when it reaches its final stage it's a lot smaller than when it started off and and the nucleus isn't nearly as large as it was to begin with and the DNA is really neatly packaged and compacted inside the cell's nucleus kind of like that and so this is a mature blood cell this is a mature blood cell and the process that I just drew out over here is what normal blood cell maturation looks like and we throw that word around a lot we talk about cell maturation all the time in fact in this video I must have mentioned it like five or six times already but we rarely talk about why cells go through this process of maturation so they go through this process so that at the end they can become specialized so they can become mature specialized cells and by specialized I mean that the cell is able to perform a specific task so for example who are looking at immature lymphoblasts over here by the time they were finished maturing into lymphocyte they would be able to perform certain immune functions so they'd be able to protect our body against invading organisms so that's the whole purpose of cell maturation so this amount of products stem cell continues to make more immature blood cells that then mature into these cells that are able to do their job and they might have put extensive does a really good job of doing that so that we end up with lots of new blood cells every single day but every once in a while very rarely actually this hematopoietic stem cell messes up and it makes an immature blast cell that's just weird and it's not normal and until that's the cell that I'm drawing in over here and this is the cell's nucleus then this is the DNA inside the nucleus and I know what I've drawn looks like a normal blast cell in fact it looks almost identical to all the other immature blast cells that I've drawn but it doesn't function like a normal cell specifically it doesn't mature like a normal cell so it can't move on to the next stage of development it's almost as if there's a stop sign over here stop saying and so this cell is stuck in the immature last stage right and the reason why it's stuck is because there's a problem inside the cell inside the cell's nucleus where one of these genes or segments of DNA becomes mutated and that gene is usually very important for helping the cell mature so that when the gene becomes mutated and it stops working the way that it should this cell then stops maturing the way that it should and that's the first thing that happens in leukemia this immature blast cell loses the ability to mature and if that was the only thing that happened in leukemia to be completely honest it wouldn't be that big of a deal so if one cell can't mature it's really not the end of the world but then unfortunately this cell acquires another mutation okay and I'm putting that in a different color and this time the mutation is in a gene that's really important for controlling cell division so that when that gene becomes mutated and it stops working the way that it should these cells lose control of how many times they can divide and that leads to a picture like this where you end up with lots of these immature blast cells accumulating and piling up and as you can see these these cells that are piling up have the same mutations as that original weird blast cell so they too are unable to mature and they're dividing rapidly and out of control okay so when we talk about leukemia this is the process that we're talking about we're talking about an immature blast cell right our leukemic cell that first loses the ability to mature and then loses control over how many times it can divide and because of that you end up with a situation where you have lots and lots of these immature blood cells and very few of these mature specialized cells okay and so you guys might be saying well that's not a problem the amount of what exam cell can can then just create some more normal blast cells that will mature and make up for the shortage in in our mature specialized cells and you'd be completely right the hematopoietic stem cell should be to create more normal blast cells but it doesn't and to explain why it doesn't we have to take a look at bone marrow so imagine that we were looking at bone marrow over here and this was a population or a group of normal blood cells and then on this side we have our weird leukemic blast cells okay that we said aren't able to mature and we also said that they start dividing very rapidly so that very quickly leads to these leukemic cells taking over the bone marrow and that's a problem because bone marrow is a contained cavity so there's a very limited amount of space nutrients and growth factors and these cells inside the bone marrow are constantly competing for these resources so as you can probably imagine if these leukemic cells are dividing really rapidly they take up all of these resources for themselves and they leave behind very little for all the other cell types and that's why the hematopoietic stem cell doesn't create more normal cells it's because it doesn't have the space the nutrients and the growth factors to be able to do so so that's why when you have a patient with leukemia if you take a look inside their bone marrow you see that the bone marrow is almost over taken by these leukemic blast cells and you see a decrease in the number of all the other types of cells so you see a decrease in the number of red blood cells and you see a decrease in the number of platelets and decrease in the number of white blood cells and really this decrease in the number of all the other types of cells is why leukemia is as devastating of a disease as it is so going back to our diagram over here there's one big question one glaring question that I feel we haven't yet addressed and that is number one how does a gene become mutated and number two how the heck did this one cell end up with two gene mutations okay so I want to talk about gene mutations and how you can get gene mutations off onto the side and one of the causes of gene mutation is something you may have heard of before and that's exposure to radiation exposure to radiation because we know radiation damages DNA um another thing is exposure to certain chemicals and toxins that also damage DNA and those are called carcinogens so exposure to carcinogens will also cause gene mutations and both exposure to radiation and carcinogens will usually cause an isolated mutation in DNA so for example if this was a strand of DNA and it was exposed to radiation or carcinogens you'd usually end up with one one gene being mutated okay a third thing that can lead to gene mutations that's really important in the case of leukemia is chromosome translocations so chromosome translocation and a translocation is an error or a mistake that's made during cell division where one part of a chromosome becomes shifted or translocated onto another chromosome so something like that and because in this case we're messing around with segments of chromosomes you end up with multiple genes being affected so instead of just one gene you can end up with mutations in two or more genes and lots of leukemias are associated with chromosome translocation and that's why this cell very easily ended up with two gene mutations and that's how leukemia develops