Mitosis

How do your toes grow?

A cell gets big. the cell splits in half. Now you have two cells

This process of growth through cell division is the only way you grow

This process, that happens in your toes, is called Mitosis

All growth from after the moment of conception is through Mitosis

This Salamander will through Mitosis

To make new Toe cells, and new cells in general the cell has to get big then split

When the cell splits all of the things needed for the new daughter cells need to be on each side of the spit

There needs to be mitochondria on both sides, Endoplasmic reticulum, golgi and Nuclei

The cell needs to have two nuclei before the split

So it we need one nucleus to become two nuclei, then all of the DNA inside needs to be copied so that the two nuclei have the same DNA. The replicating of DNA strands from 1 double helix to 2, is called DNA replication

DNA replication

To make another cell, all the DNA in the first cell needs to be copied

This involves 2 proteins 

The DNA is semi-conservative - this means that two make 2 strands of DNA each new strand is half old strand. 

Have a look at the diagram below - you can see Helicase unzipping the DNA and DNA polymerase making a new half chain by matching the nucleotides to the opposite half chain - ultimately two halves make a whole chain. This whole chain will be half old and half new.

Chromosome numbers during DNA Replication

 DNA replication occurs during a part of the Cell Cycle called Interphase

This is the longest part of the life of a cell

All 46 chromosomes, or 23 pairs, are copied. Thus the cell actually has 92 chromosomes inside its nucleus!!

So that is 4 of each numbered chromosome!!

A non-copied chromosome looks like a thick line

A copied chromosome has the stereotype X shape

So the chromosome starts off as a Chromosome 

It then replicates into two, but these are stuck together in the center -the center is called the centromere - here the whole thing is still called a chromosome. However, the two parts of the X are called chromatids or sister chromatids

Then they are pulled apart during mitosis. When the sister chromatids are separated they are now known as individual chromosomes. Daughter chromosomes. 

So

One Chromosome duplicates and becomes sister chromatids with itself whilst stuck at the centromere. But then when pulled apart, it becomes its own daughter as does its sister. 

Its sister is now its daughter.... hmmm

Cell Cycle 

Click through this overview of the cell cycle. Click on Mitosis too 😁

The life cycle of a cell is called the Cell cycle

The newly formed daughter cell, created at the end of mitosis is smaller than the original parent cell. So it must grow. This phase is called the Gap Phase - It is also the Interphase phase

Interphase is everything that is not PMAT

So Interphase includes G1, S, G2

For Y11 we don't need to know about G1 or G2. We just call it all Interphase

So a cell is either doing Interphase or it is doing Mitosis

So for almost all of its life, a cell is doing .... Interphase! 

G1 is called G1 because it is the first gap. The cell grows here

Once the cell is fully grown, the DNA is duplicated - this is called the S phase - but you wouldn't know it because you cant see it

This duplication does not result in visible chromosomes

This duplication is just so that when the cell is ready for cell division, the DNA is also ready

The Cell continues with its life, growing a bit more and getting itself ready for Mitosis. This second, Gap phase is called G2 or Gap 2

Finally, Mitosis occurs - PMAT - and one cell becomes 2!!

Collectively: G1, S Phase and G2 are called Interphase 

A nice overview, have a watch

Mitosis

Mitosis is cell division

To do this, the cross shaped chromosomes are pulled apart

These cross shaped chromosomes are cross shaped because they are the original chromosome plus a copy of that chromosome stuck together at the middle

So the two sides of the cross are identical

Each side of the cross is called a chromatid

When they are pulled apart one chromatid goes to one side of the cell and the other to the other side of the cell

It is shown on the sliding doors that open to lower levels of the Science building

Once a chromatid is on either side, then the cell splits in half and two new cells have been created

Each cell has the exact same DNA

 If we look at how the cell pulls these chromatids to either side of the cell to make two identical chromosomes and two identical cells we find that there are steps

These steps are called Prophase, Metaphase, Anaphase and Telophase

These steps follow on from the long Interphase during which the DNA had been copied and the two identical sister chromatids had been created from the original one chromosome

The process of the cell dividing is called Cytokinesis (cell movement)

So if we include Interphase and Cytokinesis, then the steps are:

Interphase, Prophase, Metaphase, Anaphase, Telophase, Cytokinesis

We can just use the first letter of each had then it becomes

  I P MAT C

Or as I like to say: I pee Mat, see

 This clip from Veritasium on Mitosis is amazing - watch it :-)

The steps of Mitosis 

 Interphase, Prophase, Metaphase, Anaphase, Telophase, Cytokinesis

The Steps of Mitosis spell "I P Mat C" 

Like "I Peed on the Mat, see" 

Interphase

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

Mitosis Interactives

Also, click through the animation below 😊

I quite like this Mitosis song 😁 

Very detailed Cell Cycle pages

Below is an interesting page on the cell cycle - it has more detail than you need. But still, have a look over it 😊

Below is another interesting page - have a look over it 😊

Mr Cowley Lectures on Mitosis