Mitosis - 2.1, 2.2, 2.3

Hi, My name is Dr Matt Ivory.

I'm a lecturer in the School of

Pharmacy and Pharmaceutical Sciences at Cardiff University.

And in this series of talks, we're going to look at the process of cell division,

so both in terms of mitosis and what is involved in that.

And we'll look at unregulated cell growth and cancer that can result from that.

And then we'll look at growth in both plants and animals as multicellular organisms

and the importance of stem cells and those processes.

So in this first talk, we're going to dig down into mitosis as a process.

So within multicellular organisms, cells aren't immortal.

So occasionally cells will die from damage or from disease.

But even if they don't, they won't last forever

as an individual cells.

So the body needs a way to provide new cells,

and they do so by undergoing cell division.

And that creates new cells that can replace lost ones.

But it can also allow the organism to grow.

So most growth in animals is through the production of

more cells to rather than our individual Selves getting bigger,

we just have more cells,

and so an increasing cell number leads to an increase

in mass of the organism and creates a bigger organism.

So in the case of single celled organisms,

a sexual reproduction occurs via mitosis as well.

So not only does that allow multi cellular organisms

to maintain their cell number and to grow,

but it also allows single celled organisms to reproduce.

So if you think about bacteria, it cells divide into two.

And that's how it's population grows.

So the process of mitosis we've touched on previously and talk about mitosis,

and you may remember that mitosis if you think about it as my t o sis,

that the T stands for two daughter cells.

So the net result of the process of mitosis

is creating to genetically identical copies of a cell,

each with a full set of chromosomes

and mitosis forms part of the cell cycle. So the normal life processes of a cell

and the first stage in the cell cycle

is called interphase,

so a normal human body cells or non gammy cell,

will have 23 pairs of chromosomes in their nuclei.

So that's 46 chromosomes, one of each type of chromosomes to make a pair,

so they're called deployed cells die meaning to,

and so in interphase, it's the phase where the cell spends most of its time,

and so during that time it will accumulate nutrients.

It will make new organelles things like mitochondria and ribosomes,

and it will perform the tasks that are required of it within the body.

So if it's a light sensing cells of the eye, it'll be sensing like during this time.

So during interphase, the cell will double its number of chromosomes.

So it undergoes DNA replication,

creating a copy of all of the DNA within the nucleus.

And it does so in preparation for mitosis,

and so by ensuring that it has double the

normal amount when it divides into two cells,

each of those cells will have the normal amount of DNA within it.

So when it undergoes this DNA replication, the duplicate D. N A.

Is paired with the original copy,

so it forms X shaped chromosomes that are identical on both arms of the X.

When the cell is ready to divide,

it moves from interphase into mitosis,

and there's a couple of different ways that people classify

mitosis so some people consider it separate to psychokinesis,

which we'll talk about more in more detail later,

but some people consider it just an all inclusive process.

But under either classification, mitosis has multiple stages within it.

So having left interface and started the process of mitosis,

the cell moves into pro phase.

So in this stage the chromosomes condense so they become shorter and Fatah

and the nuclear membrane breaks down.

And this allows the chromosomes to float out of what was the nucleus

into the cytoplasm of the cell.

And at the same time, spindle fibres are forming

and these are important structures involved

in separating the chromosomes later on.

So once this is done, the cell moves into meta phase, and in meta phase,

the chromosomes line up at the centre of the cell

and they align on the cell spindle fibres.

Once they're aligned, the cell moves into a new phase, and in Anna phase,

the two identical arms of the X shaped chromosomes are pulled apart.

And this means that one copy,

because you remember the two arms are identical to another.

One of each copy is pulled apart and moves towards the opposite ends of the cell,

and they do so along the spindle fibres.

Once they've moved, the cell moves into tele phase.

And in tele phase, a new nuclear membrane forms around each set of DNA,

so half of the doubled D N A.

And so a complete set that's needed for a cell.

So at the end of tele phase, the cell now has to complete nuclear within it.

So finally, the final stage of cell division is psychokinesis,

whether you consider it part of mitosis or not, um, and in this stage,

the cell membrane starts to form a divide between the

two halves of the cell that each contain a nucleus.

So in doing so, it obviously separates the two nuclear,

so there's only one in each of the new cells that be formed.

But it also divides things like the nutrients that are in the cytoplasm,

the organelles, things like ribosomes and mitochondria,

so that each new cell will have the stuff that it needs

to survive on its own after its kind of sealed off.

So once that cell membrane does move all the way

around and completely divides the two halves of the cell,

they are separate from one another.

They'll move apart. They are genetically identical daughter cells.

So the two of the two cells both have exactly the same DNA in them,

and they have all the nutrients and organelles that they need

to survive.

So each of these new cells will now begin interphase.

So because they are slightly less massive than the cell that produced them,

obviously the cell lost half its mass to each of the new cells.

They begin to accumulate nutrients to build more organelles, um,

and to get ready for future rounds of mitosis so the cell cycle starts once again.