captions are on! click the cc button at bottom right if you wish to turn them off. follow us on twitter (@amoebasisters) and facebook! we’ve mentioned a lot about specializedcells. specialized plant cells. specialized animal cells. so many kinds of specialized cells…it’sgoing to get a bit crowded here. but have you ever wondered…how do they getspecialized? how does a neuron or a muscle cell have thestructure and function they have? i mean, can you imagine if they had to switchjobs for a day?
that…wouldn’t go so well. they’re so specialized for the functionthey perform. well this video is going to talk about howcells differentiate into other cells, which basically means, how cells become specialized. remember that many multicellular organismslike a plant…or you…well these organisms come from a fertilized egg cell. so as a human, you started as a fertilizedegg, otherwise known as a zygote. well that zygote divides to make more cells. and more cells.
oh look, it’s a morula. oh look, it’s a blastocyst now. you know, the problem is…if the cells justkeep dividing, if you remember from our mitosis video…that makes identical cells. well that’s great for growth…and so dividingis definitely going to happen. but that’s not going to result in differentspecialized cells with different specialized functions because this cell division makesidentical cells. there’s something else that will be happeningfor that. so let’s look at that in a bit of detail.
we’re going to pause in this blastocyststage. this blastocyst contains stem cells. and these stem cells are amazing. see, they’re not differentiated yet. they’re not specialized. they are like blank slates. they don’t have a special structure. they don’t have any special job. they can become any type of body cell.
now a reminder about body cells in your body. they all---- with a few exceptions---containall of your dna. so neurons and muscle cells in your body don’thave different dna; they use different parts of the dna. genes are regulated which means they can beturned on and…off. that’s important to understand because that’sa big part of how these stem cells are going to specialize. stem cells will activate certain areas ofthe dna in their process of differentiating into certain types of cells.
transcription factors are major key playershere. they’re typically---but not always---proteinsand they determine which areas of the dna code will get transcribed into mrna, whichthen can eventually be used to make specific proteins that can impact what a cell willlook like and what a cell will do. that means transcription factors have a majorrole in determining which genes are expressed in a cell because a cell that is going tobecome a skin cell is going to have different areas of genes expressed then a cell thatis going to be a …stomach cell. there are internal and external cues for stemcells which can involve these transcription factors.
examples? ok an example of an internal cue could betranscription factors present in the cytoplasm of the original starting zygote cell---whichwill eventually be present in the cells that originate from it. the specific location of the stem cell withinthe developing embryo can matter, because the transcription factors available in differentareas of the developing embryo can differ in quantity and type, which could impact whata stem cell differentiates into. external cues could involve cell signalingfrom other cells next to it…or external cues can even be environmental effects liketemperature.
there’s still a lot of research in thisarea, and we can’t wait to see what scientists discover about this in the next decade. so stem cells are the unspecialized, undifferentiatedcells that can become other cells in your body. but not all stem cells are found in a developingembryo. stem cells can also be found in your bodyas well like your muscle, skin, liver, or bone marrow just to name a few. these are often called somatic stem cells. to give some relevance to this: it’s likelyyou have heard of bone marrow transplants
before. well bone marrow transplants actually involvetransplanting a portion of healthy bone marrow---which does contain bone marrow stem cells---withthe idea that those donor stem cells can help regenerate different types of blood cellssince bone marrow is like…a blood cell making machine. it contains stem cells that differentiateinto different types of blood cells. many---but not all--- of the somatic stemcells that are found in your body are considered to be multipotent. that means they can become many types of bodycells but not as many as the embryonic stem
cells. so, after talking about these stem cells,why the heavy focus on these stem cells right now in research? well one reason---of many---is that thesecells have the ability to differentiate into other cells and therefore they could be usedto helped regenerate organs or tissues that are damaged from a disease or an accident. there are two important issues to consider,however. one is the ethical issue, especially if consideringembryonic stems cells. the ethical issue is significant because theextraction of embryonic stem cells results
in the demise of the embryo. a point consistently debated is the potentialbenefits offered in stem cell research versus the onset of personhood of human embryos. a second issue is that organ or tissue developedfrom stem cells that didn’t come from that person will carry the risk of organ or tissuerejection, as you can get in donated organs or tissue. but here’s something promising. some research shows that somatic stem cellsfrom your own body may actually be able to develop into more types of cells than whatpeople first thought.
in fact, it was discovered that some somaticstem cells can be induced to go back into a pluripotent state…they’re what we callinduced pluripotent stem cells (ips). that means a person’s own stem cells potentiallycould then be induced into a pluripotent state…with the potential that they could differentiateinto tissues or organs that the person may need. theoretically, this could be an alternativeto waiting for an organ or tissue donor- as well as decrease chances for organ/tissuerejection since the organ or tissue would have originated from the person’s own cells. we encourage you to keep up with the topicof stem cells to stay educated on this topic---all
of our understanding of these undifferentiatedcells is likely to advance in the near future. well that’s it for the amoeba sisters andwe remind you to stay curious!
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