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  • Today's topic is the cell cycle and mitosis. But before we get into the cell cycle and

  • mitosis, we want to be sure to talk about why these words are important and how they

  • relate to real life. So if I say the word cancer, this words probably means something

  • to you. Either you know somebody who has been diagnosed with cancer or you've heard about

  • it on the news. There's many different types of cancers but one thing they all have in

  • common is that they are caused by uncontrolled cell growth. That means, someone's own cells

  • grow out of control. Now, that doesn't mean that there aren't other contributing factors

  • for example for some cancers having genetic links, meaning it runs in the family, can

  • make someone more likely to develop it, or having excessive exposure to UV light for

  • some cancers. Those are risk factors that can increase your risk. But the main cause

  • of cancer is uncontrolled cell growth. That also means it's something that it is not contagious

  • and that it's something that anyone can develop.

  • You have to realize that all the cells in your body are very busy. And they're either

  • in one of two different phases. They are either in a phase called interphase and during interphase

  • they are just growing, replicating DNA, their doing their cell functions or they are in

  • mitosis. Mitosis is a fancy word that means they are dividing, they are making new cells.

  • If you think about the cell cycle, whether they are in interphase or mitosis, it's kind

  • of like a pie graph. They are spending about 90% of their time in interphase. Most of the

  • time cells are not dividing, most of the time they are in interphase, they are growing,

  • they're doing their daily cell functions and they are replicating their DNA. Most of the

  • time, not dividing. Now, depending on what kind of cell, it might do mitosis more or

  • less often; for example, your hair follicle cells, they do mitosis frequently which is

  • why your hair can grow up to half an inch every month. But other cells like for example

  • your brain cells, your neurons, some of them do not perform mitosis, which is why if you

  • have some type of major injury to the spinal cord or to the brain, sometimes those do not

  • heal very well because those cells do not replicate.

  • So mitosis is very important to generate new cells, which can help with growth and also

  • if you damage your cells. If you're walking down the street and you have some kind of

  • accident, and you skin your knee, well you're going to need to repair those damaged cells.

  • You're going to need to be able to mitosis to repair those cells. The thing is you don't

  • want your cells to be always doing mitosis because if their always doing mitosis, then

  • they are always dividing and then they're not carrying out their actual function and

  • that's a problem.

  • That's where check points come in handy. See, along the cell cycle there are check points

  • to check that the cell is growing correctly and replicating it's dna correctly and doing

  • everything it's supposed to correctly before it divides. And what happens if the cell fails

  • it's check point? The cell does something called apoptosis which basically means the

  • cell destroys itself, it self-destructs. This might seem kind of harsh but actually it's

  • really important because it ensures you don't have these cells that are messed up continue

  • on and divide. You don't want damaged cells to continue on and divide because they might

  • do not do what they are supposed to, they might start to grow out of control, they might

  • not be regulated correctly.

  • That's where cancer cells come in. See cancer cells, as we had said, are your body's own

  • cells that are growing out of control. So they are not following the rules of these

  • checkpoints, they are flying past the check points going through the cell cycle and frequently

  • doing mitosis, which means they are dividing very, very often. And so by doing that they

  • can grow into these things called tumors which are really a mass of cancer cells. So we're

  • not really sure what causes them to escape these check points. There are a lot of factors

  • that a person can have that will increase their risk of this happening, but when these

  • cells get past these check points and grow out of control, they become a problem. Because

  • many times they can travel through the bloodstream, they started growing out of control, the body

  • can't identify them and destroy them with the immune system and so this becomes an issue

  • and usually one the treatments that someone with cancer will go through is called chemotherapy.

  • And this works by targeting cells that go through the cell cycle quickly and hit mitosis

  • quickly. And that's one reason why many people will lose their hair when they are on chemotherapy

  • because their medication that's targeting fast growing cells and their hair follicle

  • cells are also fast growing cells.

  • Cancer cells have some other factors that make them difficult to treat. One is that

  • cancers have the ability to secrete their own growth hormone. This is very bad because

  • growth hormone in the sense, think of it as a hormone that says, "FEED ME." What happens

  • is the blood vessels will divert over to those cancer cells and supply the cancer cells with

  • nutrients. This is not good because it means the cancer cells will have the nutrients they

  • need to keep growing out of control. It also can take nutrients away from nearby healthy

  • cells. There are some medications that are being researched that maybe could stop the

  • growth hormone from cancer cells and in the sense that would be great because the cancer

  • cells would not be able to get the nutrients to grow out of control. Of course, you have

  • to make sure the medication is targeting just cancer cells and that hurting the growth hormone

  • of nearby healthy cells. You wouldn't want that. So it's kind of a tricky situation.

  • So let's recap what we talked about today. We talked about the cell cycle, how cells

  • are more frequently in interphase than in mitosis. Interphase is when cells are replicating

  • their DNA or their growing, and carrying out cell processes. In mitosis, the cells are

  • actually dividing. We talked about how during this cell cycle there are checkpoints that

  • regulate the cell and keep the cell from being able to continue on if it's damaged...unless

  • we're talking about cancer cells which are cells that have escaped the checkpoints and

  • are growing out of control. Be sure to check out our clip on mitosis. This process is really

  • fascinating, but it's also a really important one in order to understand how your body cells

  • work. That's it for the Amoeba Sisters, and we remind you to stay curious!

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細胞週期與癌症 (The Cell Cycle and Cancer)

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    Amy.Lin 發佈於 2021 年 01 月 14 日
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