Cell Division Bozeman Science English English (auto-generated)

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Hi. It's Mr. Andersen and in this video I'm going to talk about cells.

hi it's mr. Andersen and in this video I'm going to talk about cells life is

Life is made of cells. It's the basic unit of structure and function. And also all cells

made of cells it's the basic unit of structure and function and also all

we have must come from preexisting cells. And so how does that work? It's through a

cells we have must come from pre-existing cells and so how does that

process called cell division. This is going to occur in all cells, both prokaryotic like

work it's through a process called cell division this is going to occur in all cells both prokaryotic like bacterial

bacteria and eukaryotic like you. And through cell division one cell can become two. Which

and eukaryotic like you and through cell division one cell can become two which

can quickly become four and then eight and then sixteen. And so we get exponential growth

can quickly become four and then eight and then 16 and so we get exponential

in cells. And to give you an idea how quickly this goes, you started life as one fertilized egg. Or one zygote. But those were quickly dividing over time. And it eventually created

growth in cells and to give you an idea how quickly this goes you started life as one fertilized egg or one zygote but those were quickly dividing over time

an adult that's going to have around 10 trillion cells inside your body. And they all came

and it eventually created an adult that's going to have around ten trillion cells inside your body and they all came

from that original cell. Now to even increase that number quite a bit, just look in your

from that original cell now to even increase that number quite a bit just

gut and we're going to find that the bacteria living in your digestive tract are going to

look in your gut and we're going to find that the bacteria living in your

outnumber the cells in your whole body ten to one. There are going to be 100 trillion

digestive tract are going to outnumber the cells in your whole body ten to one they're going to be a hundred trillion

bacteria just living in your gut. And they're going to be outnumbered about 10 to one by

bacteria just living in your gut and they're going to be outnumbered about

viruses living in your gut. So we're going to have quadrillion viruses living in your

ten to one by viruses living in your gut so we're going to have quadrillion

gut. Now viruses aren't technically cells, but everything else I've described here is

viruses living in your gut now viruses aren't technically cells but everything else I've described here is

going to be reproducing or it's going to be created through a process called cell division.

going to be reproducing or it's going to be created through a process called cell

And there are really three types of cell division. In prokaryotic cells, or in bacteria, they're

division and there are really three types of cell division in prokaryotic cells or in bacteria they're simply

simply going to divide through a process called binary fission. That's where one cell, one

going to divide through a process called binary fission that's where one cell one

bacteria cell, is going to make two cells that are exact copies of the original cell.

bacterial cell is going to make two cells that are exact copies of the

In eukaryotic cells we have something similar to this. We're going to have cell division

original cell and eukaryotic cells we have something similar to this we're

or we sometimes just refer to it as mitosis. Technically mitosis is going to be division

going to have cell division or we sometimes just referred to it as mitosis technically mitosis is going to be

of the nuclei. And then we're going to have cytokinesis which is division of the rest

division of the nuclei and then we're going to have cytokinesis which is

of the cell. But we generally just say mitosis is when one eukaryotic cell makes two cells

division of the rest of the cell but we generally just say mitosis is when one eukaryotic cell makes two cells that are

that are exact copies of that cell. It's a lot like binary fission. And then the third

exact copies of that cell it's a lot like binary fission and then the third

type of cell division is going to be meiosis. Meiosis is going to be when we create sex

type of cell division is going to be meiosis meiosis is going to be when we

cells. Or when we create gametes. Mitosis and binary fission insure that we have exact

create sex cells or when we create gametes mitosis and binary fission in

duplicates of that original cell. Meiosis is totally different. Meiosis is going to

were that we have exact duplicates of that original cell meiosis is totally

make cells that are different. They're going to have half the genetic information and they're

different meiosis is going to make cells that are different they're going to have half the genetic information and they're

going to give us variability. And so in us sex is important because it gives us variability

going to give us variability and so in us sex is important because it gives us

in the next generation. In bacteria mutation and there's some other ways that they can

variability in the next generation in bacteria mutation and there are some

share information is more important. So let's start by talking about bacteria. They reproduce

other ways that they can share information is more important so let's start by talking about bacteria they

through a process called binary fission. In this we're going to have this adult cell,

reproduce through a process called binary fission in this we're going to

so we're going to have this parent cell. It's going to be made up of, you can see here,

have this adult cell so we're going to have this parent cell it's going to be made up of you can see here ribosomes

ribosomes. It's going to have a plasmid here which is a little bit of extra DNA. But it's

it's going to have a plasmid here which is a little bit of extra DNA but it's

genome or all of its DNA is going to be wrapped up into one loop. And so what do we want to

genome or all of its DNA is going to be wrapped up into one loop and so what do

do in binary fission? We want to take one cell and we want to make two cells that are

we want to do in binary fission we want to take one cell and we want to make two

identical to that. And so the process is pretty simple. What the bacteria cell starts doing

cells that are identical to that and so the process is pretty simple what the

is duplicating all of its DNA. So the first thing it will do is DNA polymerase goes around

bacterial cell starts doing is duplicating all of its DNA so the first thing it'll do is DNA polymerase goes

the whole loop and it's going to make an exact copy of all the DNA in the bacteria. One thing

around the whole loop and it's going to make an exact copy of all the DNA in the bacteria one thing not shown in here is

not shown in here is that we're also going to duplicate our plasmids. And we're also

that we're also going to duplicate our

going to have, you know, ribosomes increasing as we increase the number of DNA as well.

plasmids and we're also going to have you know ribosomes increasing as we increase the number of DNA as well what

What happens next is it's going to be pulled to the side of that cell. And really what's

happens next is this going to be pulled to the side of that cell and really

going to happen is the DNA will actually attach to the cell wall. And then eventually that

what's going to happen is the DNA will actually attach to the cell wall and

cell wall is going to split in half and we're going to have two bacteria cells. How are

then eventually that cell wall is going to split in half and we're going to have two bacterial cells how are they

they different? They're not really different. They're exactly the same. The DNA in this

different they're not really different they're exactly the same the DNA in this

cell and the DNA in this cell is going to be exactly the same. And when we divide in

cell and the DNA in this cell is going to be exactly the same and when we

half, we're going to divide in half those ribosomes and the plasmids as well. And so

divide in half we're going to divide in half those ribosomes and the plasmids as

again, bacteria don't do mitosis. They don't have sex. They simply reproduce through binary

well and so again bacteria don't do mitosis they don't have sex they simply

fission. And this happens incredibly quickly. So in a typical e. coli they can copy themselves,

reproduce through a binary fission and this happens incredibly quickly so in a typical ecoli they can copy

make two copies of one cell, in 20 minutes. Which is just crazy how fast that occurs.

themselves make two copies of one cell in 20 minutes which is just crazy how fast that occurs but again we don't go

But again we don't go through binary fission because we're eukaryotic cells. And before

through binary fission because we're

we talk about mitosis and meiosis, we should make sure you know the difference between

eukaryotic cells and before we talk about mitosis and meiosis we should make

what a gamete is and then a somatic cell. And so eukaryotic cells are going to be everything

sure you know the difference between what a gamete is and then a somatic cell and so eukaryotic cells are going to be

from the chimpanzee to the bees to the flowers to the mushroom to the yeast, they all have

everything from the chimpanzee to the bees to the flowers to the mushroom to yeast they all have a nuclei and so

a nuclei. And so there are two types of cells that we find inside eukaryotic organisms.

there are two types of cells that we find inside eukaryotic organisms first

First are going to be the somatic cells. Somatic cells are going to be the body cells in your

are going to be the somatic cells somatic cells are going to be the body

body. And then we're going to have the gametes which are going to be the sex cells. So in

cells in your body and then we're going to have the gametes which are going to

humans the only cells inside our body that are going to be gametes are going to be sperm

be the sex cells so in humans the only cells inside our body that are going to be gametes are going to be sperm in

in males and then the eggs or the ovum that are found inside females. How are they different?

males and then the eggs or the ovum that are found inside females how are they

Remember somatic cells are the body cells that are going to be diploid in humans. They're

different remember somatic cells are the body cells are going to be diploid in humans

going to have two copies of every gene. And therefore two copies of every chromosome.

they're going to have two copies of every gene and therefore two copies of every chromosome gametes are only going

Gametes are only going to have one. So sperm and egg each provide you with half the DNA

to have one so sperm and egg each provide you with half the DNA that you

that you get. So how do we duplicate a typical cell? Well first we should say when do we

get so how do we do plate duplicate a typical cell well first we

do that? Well remember when you go from a zygote to an adult, we're doubling the cells

should say when do we do that well remember when you go from a zygote to an adult

over and over and over again. And then we're constantly replacing the cells in our body.

we're doubling the cells over and over and over again and then we're constantly replacing the cells in our body so as

So as cells become worn out or damaged or removed we have to replace those with other

cells become worn out or damaged or removed we have to replace those with

cells. And we do that through mitosis. Again what is mitosis? It's technically the division

other cells and we do that through mitosis again what is mitosis it's technically the division of the nuclei

of the nuclei, but then we're going to have division of the rest of the cell which is

but then we're going to have division of

called cytokinesis. So what do we start with? And we're going to make this real simple,

the rest of the cell which is called cytokinesis so what do we start with and

this is a simple cell. It's a diploid cell. It's 2n=2. That means they have two chromosomes.

we're going to make this real simple this is a simple cell it's a diploid cell it's 2n equals two that means they

These two chromosomes are going to be homologous. That means that they're the same length. The

have two chromosomes these two chromosomes are going to be homologous that means that they're the same length

reason why they're different colors is you get on from one parent and one from another.

the reason why they're different colors is you get one from one parent and one

And so in mitosis, let's look first before we talk about the specifics of what we're

from another and so in mitosis look let's look first before we talk about

going to get out of mitosis. We're going to start with one cell looks like this. And we're

the specifics of what we're going to get out of mitosis we're going to start with one cell looks like this and we're going

going to end up with two cells that look exactly like that first cell. So in mitosis we want

to hit ten end up with two cells that look exactly like that first cell so in

to duplicate the cell. And so let's watch that. What's the first thing that happens

mitosis we want to duplicate the cell and so let's watch that what's the first

is we have to duplicate all of the DNA. And this occurs during interphase. What's going

thing that happens is we have to duplicate all of the DNA and this occurs

to happen is this chromosome right here is going to copy all of its DNA. And now we're

during interphase what's going to happen is this chromosome right here is going to copy all of its DNA and now we're

going to have what are called sister chromatids. And so we have a chromosome on this side.

going to have what are called sister chromatids and so we have a chromosome

A chromosome on this side. And they're exactly the same. So they're an exact duplicate of

on this side a chromosome on this side and they're exactly the same so they're an exact duplicate of that original

that original chromosome. And you can see that we're going to have that on the other

chromosome and you can see that we're

homologous chromosome as well. What happens next? They're going to meet in the middle.

going to have that on the other homologous chromosome as well what happens next they're going to meet in

They're going to line up. These lines represent a spindle which is going to attach to either

the middle they're going to line up these lines represent a spindle which is

side. Each of those sister chromatids and then they're going to be pulled apart. They're

going to attach to either side those sister chromatids and then they're

going to be pulled apart. And eventually, so this would be the mitosis when we divide

going to be pulled apart they're going to be pulled apart and eventually so this would be the mitosis when we divide

the nuclei. And then the whole cell is going to split in half. We're going to divide that

the nuclei and then the whole cell is going to split in half we're going to

cytoplasm and that's called cytokinesis. And so what do we end up with? We end up with

divide that cytoplasm and that's called cytokinesis and so what do we end up

two cells that are both diploid. Our original cell was diploid as well. So let's take a

with we end up with two cells that are both diploid our original cell was diploid as well so let's take a look at

look at what this really looks like. We're looking right here at cells that are undergoing

what this really looks like we're looking right here at cells that are

mitosis. And so they're growing on a growth medium. And if we just play the video, this

undergoing mitosis and so they're growing on a growth medium if we just

is time lapsed. And so it's speeding it up quite a bit. But what will happen if we look

play the video this is time-lapse and so it's speeding it up quite a bit but what

at like this cell right down here, is that you can see it kind of come together in the

will happen if we look at like this cell right down here is that you can see it

nuclei's dividing up the genetic information. And then the rest of the cell is going to

kind of come together and the nuclei is dividing up the genetic information and then the rest of the cell is going to

divide. What do we end up with when we're done with that? We have two identical cells.

divide what do we end up with when we're done with that we have two identical

And those are going to grow. And then they're eventually going to divide the nuclei and

cells and those are going to grow and then they're eventually going to divide

they're going to grow. And they're going to grow. And they're going to grow. And cells,

the nuclei and they're going to grow and they're going to grow and they're going

unless they're cancer cells, are going to keep growing on here until they fill up this

to grow and cells unless they're cancerous cells are going to keep growing on here until they fill up this

whole medium. But we need to talk about meiosis, which is the third type of cell division.

whole medium but we need to talk about meiosis which is the third type of cell

What happens in meiosis. Meiosis is when you take one cell and we're going to make four

division what happens in meiosis meiosis is when you take one cell and we're

cells out of it. Now let's look how this is a little different than in mitosis. In mitosis

going to make four cells out of it now let's look how this is a little different than in mitosis and mitosis

remember we took one cell and we made two cells. In meiosis we're actually going to

remember we took one cell and we made two cells in meiosis we're actually

have another division. But there's something even different that we didn't see in mitosis.

going to have another division but there's something even different that we

Remember in mitosis we want to make sure that each of the cells that we make are identical

didn't see in mitosis remember mitosis we want to make sure that each of those

to that original cell. You can see here that the four cells that we create at the end are

cells that we make are identical to that original cell you can see here that the four cells that we create at the end are

going to be totally different than that original cell. And they're going to have half the genetic

going to be totally different than that original cell and they're going to have

information. Remember I said the sperm and the egg have half the information that's found

half the genetic information remember I said the sperm and the egg have half the

in the original cell. And so what's going happen? Well let's watch how this begins.

information that's found in the original cell and so what's going to happen well

The first thing that happens is you're going to duplicate each of these chromosomes. And

let's watch how this begins first thing that happens is you're going to duplicate each of these chromosomes and

so we're going to make copies of the chromosomes. But then something odd happens. What happens

so we're going to make copies of the chromosomes but then something odd

that's odd, we're going to take a little bit, in the case we're going to take a little bit

happens what happens that's odd we're going to take a little bit in this case

of this white chromosome here. And it's going to cross over with this red chromosome right.

we're going to take a little bit of this white chromosome here and it's going to cross over with this red chromosome

So we're actually swapping chromosomes. And so that process is called crossing over but

right here so we're actually swapping chromosomes and so that a process is

what you're really doing is your crossing over or your making a new chromosome. It's

called crossing over but what you're really doing is you're crossing over or

a combination of the chromosome you got from your mom and your dad. It's a chromosome that's

you're making a new chromosome it's a combination of the chromosome you got from your mom and your dad

never been built before. So those will eventually line up in the middle. And then they're going

it's a chromosome that's never been built before so those will eventually line up

to divide. And then they're going to divide again. And so they'll divide in half. So this

the middle and then they're going to divide and then they're going to divide again and so they'll divide in half so

is meiosis one and then they'll divide in half again. And that is called meiosis two.

this is meiosis one and then they'll divide in half again and that's called

So what do we create when we're done. We're going to create daughter cells. But each of

meiosis two so what do we create when we're done we're going to create daughter cells but each of those

those daughter cells are going to be different. Each of these would create a new sperm or

daughter cells are going to be different each of these would create a new sperm

a new egg. Now it's going to be much more complicated in us, in humans, remember, we're

or a new egg now it's going to be much more complicated in us and humans

not going to start with 2n=4. With 4 total chromosomes here. We're going to start with

remember we're not going to start with 2n equals 4 with four total chromosomes

2n=46. And so we're going to start with 46 chromosomes. So it's going to be really really

here we're going to start with 2n equals 46 and so we're going to start with 46 chromosomes so it's going to be really

different when we get to the end. And so we can create literally billions and billions

really different when you get to the end and so we can create literally billions

of different types of cells through meiosis. And so that's going to give us variation.

and billions of different types of cells through meiosis and so that's going to give us variation so to summarize what

So to summarize. What do we have? We have three types of cell division. We've got binary

do we have we have three types of cell division we've got binary fission that's

fission. That's going to be found just in bacteria where you take one bacteria, first

going to be found just in bacteria where you take one bacteria first copy the DNA

copy the DNA and then the rest of the cell is going to divide through cytokinesis. Each

and then the rest of the cell is going to divide through cytokinesis each of

of these daughter cells is going to be identical to that first cell. If you're looking at eukaryotic

these daughter cells is going to be identical to that first cell if you're

cells, we've got mitosis. What happens in mitosis? We start with a diploid cell. So

looking at eukaryotic cells we've got mitosis what happens in mitosis we start with a diploid cell so here are the Reds

here are the reds and the greens are each going to come from different parents. So we

and the greens are each going to come

have four chromosomes. They're going to duplicate first during S phase of interphase. They'll

from different parents so we have four chromosomes they're going to duplicate first during S phase of interphase

line up in the middle. And they'll be pulled to the side. Now if we look here, these two

they'll line up in the middle and they'll be pulled to the side now if we

cells that are produced in mitosis are identical to that original cell. And that's what mitosis

look here these two cells that are produced in mitosis are identical to that original cell and that's what

does. It makes exact copies. If we start with meiosis, meiosis is going to start with an

mitosis does it makes exact copies if we start with meiosis meiosis is going to

original cell that looks very similar. But instead of lining up like this where we separate

start with an original cell that looks very similar but instead of lining up

the sister chromatids, they're going to line up with the homologous chromosomes wrapping

like this where we separate the sister chromatids they're going to line up with the homologous chromosomes wrapping

around each other and swapping bits of that chromosome. They'll divide in half. And then

around each other and swapping bits of that chromosome they'll divide in half

they're going to divide in half again. And what we're going to create is gametes. Those

and then they're going to divide in half again and what we're going to create is

are going to be sperm and egg that have half the genetic information in a new combination

gametes those are going to be sperm and egg that have half the genetic information and a new combination of

of that genetic information. So again, this will be fertilized by a different sperm and

that genetic information so again this will be fertilized by a different sperm

we get back to a zygote. Where do we go from the zygote? We go right back here to mitosis

and we get back to a zygote where do we go from the zygote we go right back here

where we can copy that cell over and over and over and over again. And so that's cell

to mitosis where we can copy that cell over and over and over and over again

division. It's found in all cells on our planet. It shows how one cell can go to all the cells

and so that's cell division it's found in all cells on our planet it shows us how one cell can go to all the cell's

that we have to day. A good question might be where did that original cell come from?

that we have today a good question might be where did that original cell come

But that's for another podcast. And I hope that was helpful.

from but that's for another podcast I hope that was helpful