2.5 Cell Division

Work through this task to see some slides of the cell cycle. How long does the cell spend in each phase? Why do we use root tips for sampling cells in mitosis and not other cells? Online root tip lab from The Arizona Biology Project.

Essential Biology 2.5: Cell Division (mitosis)

Here’s a lovely mitosis video:


The Cell Cycle: Interphase (G1, S1, G2), Mitosis, Cytokinesis

Interphase is an active period in the life of cell

Mitosis is the production of two genetically identical nuclei

Genetically identical nuclei:


Many processes involve mitosis:


Tumours (cancers) are the result of uncontrolled cell division.

Correlation-cause conundrum: Link between contraceptive pill use in women and prostate cancer in men. Huh?

In this TEDMED2009 Talk, David Agus argues that we are taking too much of a reductionist approach to cancer diagnosis and treatment, and suggests that technological advances in proteomics and genomics. He makes connections here to the genetic basis of cancers, but also to the more complex environmental factors within our bodies and the idea of emergent properties of systems being more than the sum of their parts. Some of the genetics ideas will be covered later in the course, so re-watch it then.


If telomeres are part of the ageing process, then can the effects be reversed?

Ageing reversed in mice, using telomerases, from the Guardian (take this with a pinch of salt, before rushing out to buy ‘telomerase’ beauty creams!)

How do stem cells know which specialised cells to become? Check out this really cool new technique which allows researchers to track the path of individual cells in real time in embryos.


Lyrical Science: I Will Divide

A single diploid cell
Not yet specialised
Needs to find a way to multiply
To keep optimum size
Or repair damaged tissues
Or to let the organism grow
Reproduce asexually
Or develop embyros…

You know I’m eu-
-karyotic ‘cos
My chromosomes are all kept safely
Deep inside my nucleus
Through the process of mitosis
All my daugher cells will be
Genetically identical:
They’re little clones of me!

Oh yeah now pro – my centrioles
Are taking up position
At the cell’s opposing poles
And the nuclear membrane will break down and you can see
The sister chromatids
Supercoiled incredibly!

And so I
I will divide
After chromatids migrate
To the equator and align
Spindle fibres will reach out
To centromeres so there’s no doubt
That they’re all right
When I divide

In anaphase the spindle fibres
Simply pull apart
Detaching sister chromatids
And their relocation starts
These chromosomes will move
Towards the edges of the cell
When they get there
They’re all correct and safe and well!

And so Telo!
There at the poles!
Will reform a pair of nuclei
To hold these chromosomes
As the plasma membrane forms
At the equator you can see
Cytokinesis taking place
And this new membrane divides me!

And so I
I will divide
For as long as I’m instructed to
You know I will divide
And so the organism lives
All it took was mitosis
And I divide
Oh I divide


Apoptosis: Programmed Cell Death

Lyrical Science: One Ribosome – Apoptise (IB Bio remix) (based on One Republic’s Apologise). To understand this fully, you’ll need to read ahead to chromosomes, genes, alleles and mutations and to protein synthesis.

One Ribosome – Apoptise
Stem cells multiplyin’
In amongst your tissues
Dividing to make skin,
Bowel, cervix and prostate too
But with all this dividing
There’s a chance they go wrong –  mutate
Butwith programmed cell destruction
Base substitutions won’t prolif-erate
Skip the first chorus
Significant the chance
Mutation’s taking place inside of you
Higher if a mutagen affects
Multiply’n tissues – oh, no
If a gene starts to mutate
It don’t know what to do
When translate(ed)
So TP53 gene
Cannot tell mitosis to…
To terminate
Now it’s too late to apoptise – it’s too late
The codon’s  been mis-transcribed – it’s too late
It’s too late to apoptise – it’s too late
If those cells metastasise – it’s not great
Now it’s too late to apoptise – yeah
Now it’s too late to apoptise – yeah
Mitosis needs to stop
Or it will keep on going round…

This is heavily inspired by the Stanford Students’ version of Apoptise:


  1. Hi Stephen,
    I LOVE your site and thank you for helping me become a better IB Bio teacher.

    Have you seen this video on TED.com?
    Interesting new possibilities for the treatment of cancer.

    Have a look and have a fabulous week!


  2. Oops… here is the link:

  3. Hi Stephen,
    Your website is unbelievable. I’ve only started teaching IB Biology and it’s what is keeping my head above the water. Thanks.


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