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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!