Annotated Video Script TEMPLATE Cell Cycle by Amoeba Sisters

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Amoeba Sisters: Annotated Video Script Template

The Cell Cycle [and cancer]
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Video Script (informal) Questions and Sketches

Note: The informal script below has have some slight improvements from the We learn from questions! After you make a question mark in
direct transcript on YouTube. Improvements are made to define sentences the text, write your question out in this space next to it. Like
and to remove excessive filler words that can occur when speaking. By to doodle? Visual notes are great. If you come up with
making these improvements, this script is easier to annotate. However, the something that helps you remember a concept or a
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video for captioning.
“Have you ever been sitting in class and thought to yourself, ‘I

wonder what my skin cells are doing right now at this very
moment?’ This kind of pondering may be unique to
me…maybe…but wouldn’t we at some point wonder what our
cells are doing right now? If you remember, as part of the cell
theory, we are all made of cells. All living things are made of one
or more cells! Many multicellular organisms, like you, have cells
that work together. Working together as part of body tissue. Body
tissues working together as part of an organ. Organs working
together as part of an organ system. Your cells are specialized to
work in these different levels of organization. You have skin cells,
stomach cells, and muscle cells just to name a few, and their
functions need to be regulated. These cells are regulated as part of
something called the cell cycle and that is going to relate to my
question of, ‘I wonder what my cells are doing right now.’
Cells themselves can grow in size. However, a multicellular

organism isn’t growing because each individual cell is getting
bigger. A multicellular organism itself grows by making more cells,
and the cells make more cells by dividing. That’s cell reproduction.
One reason that you’re bigger than you were when you were five
years old is because your cells have divided to make more cells.
Mitosis, and the cytokinesis that follows to split the cytoplasm,
allows you to make new body cells.
Still, you don’t want that cell division happening all the time. Why?
It is likely that you have heard the term ‘cancer’ before. We have
had family members that have battled cancer, and it is definitely a
relevant topic for all of us. Cancer is in part due to cells that divide
too frequently. Cancer cells are not regulated; they are
uncontrolled. Cancer cells can have other problems too. They
might not be able to communicate with other healthy cells, and
they may not be able to carry out normal cell functions.
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Cancer cells also may not securely anchor themselves like other
cells do which can make them more likely to travel somewhere
else. Some cancer cells have the ability to secrete their own
growth hormone, which makes blood vessels divert over to those
cancer cells and supply the cancer cells with nutrients. This can
take nutrients away from healthy cells.
Why do cancer cells become this way? Well, there is a lot of

research in this area. With some cancers, there may be genetic
links making some cells more susceptible to having problems.
These genetic factors might run in families. Exposure to toxins,
radiation, or excessive exposure to UV light can be risk factors for
some cells to become cancerous. The uncontrolled growth that
cancer cells have can give rise to more cells like them, which can
develop into a tumor. Some tumors stay put, but some do not.
Fortunately, scientists continue to develop better treatments,

which include destroying the cancer cells with radiation or
medication- such as chemotherapy- which will target cells that
divide frequently. Maybe someday you will be part of helping to
meet the challenge of trying to eliminate cancer, because the fact
remains that these cells are not participating in the cell cycle
like they should.
So, what is the cell cycle? The cell cycle is often represented as a
pie chart. Cells are either in one of two different phases. They are
either in a phase called interphase where the cells themselves are
growing, replicating their DNA, and doing their cell functions; or,
they are in M phase, which includes mitosis (division of the
nucleus) and cytokinesis (actual splitting of the cytoplasm).
It is M phase where cells actually divide to make more cells. Still,

cells spend most of their time in interphase. So, most of the time,
cells are not dividing.
Now, depending on what kind of cell, it may do mitosis more or

less often. Your hair follicle cells do mitosis frequently which is
why your hair can grow at the rate that it does. This is also why
many cancer drugs may also target hair follicle cells, because many
cancer drugs go after cells that do cell division frequently.
It’s a big deal for cells to hit this M phase. If a cell has an error, a
harmful mutation for example, it can divide to create another cell
that would also have this harmful mutation. That’s where check
points come in handy. There are check points along the cell cycle
to check that the cell is growing well, replicating its DNA correctly,
and doing everything it’s supposed to do correctly before it
divides.
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To better understand those checkpoints, let’s consider the phases

in the cell cycle. We have G1 (Gap1), S (synthesis), and G2 (Gap 2).
Those phases are all part of interphase. Then we have M phase
where mitosis and cytokinesis will happen.
During G1, the cell individually itself grows.
Then the cell replicates its DNA in S phase. You can remember that
because the "s" is for “synthesis,” which means to make
something. The cell is making more DNA!
Then in G2, the cell grows some more in preparation for mitosis.
So let’s consider the checkpoints. We have a checkpoint in G1. This

checkpoint checks several factors. Is the cell growing well enough?
Is its DNA damaged? If the DNA is damaged, you definitely don’t
want it to move on to S phase where it would replicate DNA. Does
the cell have the resources it needs if it were to keep moving on?
This checkpoint in G2 checks if the DNA was replicated correctly

back in S phase. Is it growing well enough? Does it have the
resources it needs to continue?
Okay then, moving on, this next checkpoint in M phase is my

favorite checkpoint! It checks in the stage metaphase to make sure
that chromosomes, which are made up of DNA, are lined up in the
middle correctly. It checks that the chromosomes are all attached
to the spindle correctly. If they’re not, the chromosomes will not
be separated correctly.
So, now you may have two big questions. First, what happens if
the cell doesn’t meet the requirements of the checkpoint? Second,
what is doing the regulating of this cycle anyway?
To address the first question- if the reason the cell can’t go past
the checkpoint is a reason that can be fixed, the cell may kind of
pause here until it can fix the issue. What if it can’t be fixed? Then
the cell does something called apoptosis, which basically means
the cell self-destructs. This ensures that a cell that is damaged
beyond repair will not go on to divide.
So, what is doing the regulating anyway? We’ve mentioned before

that proteins are a big deal. Genes in your body can code for
proteins that do an assortment of functions, and there are many
proteins involved with regulating the cell cycle. Some of them are
positive regulators, because they allow moving forward in the
cycle. Some are negative regulators that can make things stop.
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The proteins themselves can be sensitive to cues inside and

outside of the cell. Two proteins that are involved in positive
regulation are cyclin and Cdk. Cdk is specifically an enzyme
protein---a fancy kind called a kinase which is worth researching!
Cdk can have different forms of cyclin protein bound to it.
Different types of cyclin rise and fall throughout the cell cycle, and
the rising and falling is based on a variety of signals to determine
when the cell should move on to the next cell cycle phase.
Typically each cell cycle phase---G1, S, G2, M---- will tend to have a
different cyclin binding with the Cdk. The rise and fall of cyclin
types, and the role Cdk has when it’s active, is a fascinating subject
to explore.
Remember the vocabulary word apoptosis? Proteins that are

negative regulators, such as a protein called p53 for example, can
be involved in initiating apoptosis. Again, we encourage you to
explore beyond this video.
One last thing to mention. There are some cells that don’t go
through the phases we mentioned, because they’re actually in G0.
That’s a zero by the way and not an “o,” because if it was an o,
then it’d say go and G0 is kind of the opposite of that. G0 is a
resting phase. Cells in G0 are still performing cell functions, but
they’re not preparing to divide. Some cells go here temporarily.
They may do this if there are not enough resources around for
example. However, some cells, like many types of neurons in your
brain and spinal cord, may stay here permanently. If they stay here
permanently, they’ll never get to M phase, so they will not divide.
This can be one reason why a major injury to the brain or spinal
cord can have challenges with healing as many of those cells may
not be able to replicate. This is a topic that continues to be
researched.
Well, that’s it for the Amoeba Sisters, and we remind you to stay
curious.”
Check your work!

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Page 4 of 4

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Name: __________________________________________________________

Amoeba Sisters: Annotated Video Script Template

Suggested Script Annotation Key:

Video Script (informal) Questions and Sketches

“Have you ever been sitting in class and thought to yourself, ‘I

Cells themselves can grow in size. However, a multicellular

Why do cancer cells become this way? Well, there is a lot of

Fortunately, scientists continue to develop better treatments,

It is M phase where cells actually divide to make more cells. Still,

Now, depending on what kind of cell, it may do mitosis more or

To better understand those checkpoints, let’s consider the phases

During G1, the cell individually itself grows.

So let’s consider the checkpoints. We have a checkpoint in G1. This

This checkpoint in G2 checks if the DNA was replicated correctly

Okay then, moving on, this next checkpoint in M phase is my

So, what is doing the regulating anyway? We’ve mentioned before

The proteins themselves can be sensitive to cues inside and

Remember the vocabulary word apoptosis? Proteins that are

Check your work!

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