Cell Division: Mitosis and Meiosis

Three types of cell division
Three types of cell division | Source

Cell Division Glossary

Chromosome - A molecule of DNA wrapped around histones that becomes visible during prophase of cell division.

Chromatid - A replicated chromosome: each strand of the 'X' is a chromatid.

Diploid - Cells that have two copies of each chromosome in their nuclei.

Haploid - Cells that have one copy of each chromosome in their nuclei.

Homologous Chromosomes - Chromosomes that have the same genes in the same places. For each homologous pair, one comes from the mother, the other from the father.

What are the Stages of Mitosis and Meiosis?

All living things are made of cells - this is one of the key parts of Cell Theory. In order to survive, these cells must be able to make more cells. Cells achieve this using Cell Division - perhaps one of the more complicated topics I teach my A Level Biology students.

Cell division is the process by which biological cells multiply. There are three major types of cell division:

  1. Mitosis - used by Eukaryotic organisms to grow or reproduce asexually;
  2. Meiosis - used by Eukaryotic organisms to create sex cells (gametes);
  3. Binary Fission - used by Prokaryotic organisms to reproduce.

Despite their differences, remember that all three types of cell division begin with DNA replication - the act of doubling the amount of DNA in the cell.

Teaching Tip! The stages of cell division are complex and subtle. When examined on them, try to use labelled diagrams and tables to summarise the key information. Also ensure that all key terms are used appropriately, as this can save you time and energy.

The Stages of Mitosis

Click thumbnail to view full-size
In this slide you can see the upper cell in Prophase, and the lower cell well into AnaphaseThe upper-centre cell is in interphase (nucleus still visible); the lower cell is in late metaphase/early anaphase
In this slide you can see the upper cell in Prophase, and the lower cell well into Anaphase
In this slide you can see the upper cell in Prophase, and the lower cell well into Anaphase | Source
The upper-centre cell is in interphase (nucleus still visible); the lower cell is in late metaphase/early anaphase
The upper-centre cell is in interphase (nucleus still visible); the lower cell is in late metaphase/early anaphase | Source

Mitosis Stages

Mitosis is the process of cell division that forms two genetically identical nuclei from on parent cell nucleus. It is used for:

  • Asexual reproduction (e.g. Paramecium)
  • Growth (increasing cell number)
  • Repair and Maintenance (replace damaged cells with identical replacements)

Although we traditionally break down mitosis into a series of stages and sub-stages, it is actually a continuous process. In the micrographs opposite, you can see that mitosis is not necessarily synchronised and looks much messier than the clean, idealised textbook diagrams!

Interphase - Not strictly a stage of mitosis, this is where the cell prepares to divide by growing, storing energy, replicating organelles and replicating DNA

Prophase - The chromosomes supercoil and become visible under a light microscope. The chromosomes assume their classic 'X' shape - two sister chromatids joined in the middle at the centromere. Other key events are:

  • Nuclear Envelope breaks down;
  • Centriole divides in two, travels to opposite poles of the cell to form the spindle.

Metaphase - An easy stage to identify, Metaphase is characterised by the chromosomes lining up, single file, along the middle (the equator) of the cell. At this point, each chromosome becomes attached to the spindle at its' centromere.

Anaphase - Another easily recognisable stage! Anaphase sees the chromosomes split at the centromere, separating the sister chromatids:

  • The sister chromatids are pulled apart to opposite poles of the cell
  • At this point, each chromatid becomes an individual chromosome - identical to the original parent chromosome
  • Spindle fibres shorten, pulling each chromatid by the centromere - this causes the chromatids to look like Vs

Telophase - a simple stage to recognise - you will see two nuclei starting to form in early telophase; in late telophase you will no longer be able to see the chromosomes, just two complete nuclei at opposite ends of the cell.

Interphase, Prophase, Metaphase, Anaphase and Telophase

Main Event
DNA is replicated, Cell builds up energy reseves and grows.
DNA Packaged - the chromosomes shorten and thicken
Chromosomes line up in the middle of the cell
Chromatids break apart at the centromere and move to opposite poles
Two nuclei formed after nuclear envelopes reform around each group of chromosomes
Two (nuclei)
I P on the MAT! Mitosis keeps the number of chromosomes in the nucleus the same, forms two new nuclei and produces no genetic variation - the genetic information passed to the daughter cells is identical to the parent cell.

Summary of Mitosis

Do you think it is important for High School Students to learn about cell division?

  • No - there is no relevence to everyday life
  • Yes - the skills and knowledge can be reapplied to other fields
  • Yes - to allow them the option of studying Biology at a higher level
  • No - this concept is too complicated and taught poorly by most teachers - leave for college
  • I don't know
See results without voting

The Stages of Meiosis

The stages of Meiosis
The stages of Meiosis | Source

Meiosis Stages

Human body cells have 46 chromosomes. These are arranged in pairs, with one copy of each chromosome from Mum, and the other from Dad. If your sperm and eggs were made using mitosis, when these two cells fused at fertilisation, the egg would have 96 chromosomes. Definitely not human!

Meiosis is the process of cell division that halves the chromosome number and makes gametes (human gametes contain 23 chromosomes). This ensures that at fertilisation the number of chromosomes found in normal body cells - the diploid number - is restored.

Meiosis involves two divisions of the nucleus:

  • The first division generates most of the variation
  • The second division halves the chromosome number.

Meiosis is a very technical process that is most easily described in diagrams and tables (see above and below).

A human Karyotype image.
A human Karyotype image. | Source

What are Homologous Chromosomes?

In the photo to the right, you can see all the chromosomes from a human cell. In the inset box, you see all of the chromosomes paired up according to size - this is called a karyotype. Each pair is known as a homologous pair. In each pair, one chromosome comes from Mum and the other comes from Dad.

Homologous chromosomes are:

  • The same size;
  • The same shape;
  • Have the centromere in the same place;
  • Have the same genes.

The X and Y chromosomes have only one small region that is homologous, but are still grouped together as they determine the sex of an individual.

During Crossing over, analagous sections of DNA from homologous chromosomes are swapped over.
During Crossing over, analogous sections of DNA from homologous chromosomes are swapped over. | Source

What is Crossing Over?

Crossing over (and recombination) is where homologous chromosomes exchange genetic material and create 'recombinant chromosomes.'

During Prophase I, homologous chromosomes line up with each other and swap small amounts of their DNA from similar regions. Without recombination and crossing over, all alleles on a single chromosome would be inherited together. This system creates new gene combinations which increases our capacity (as a species) to respond to environmental change.

Meiosis Summary

Key Event
Prophase I
Chromosomes condense, Crossing over occurs
Metaphase I
Homologous chromosomes pair up and align in middle of cell
Anaphase I
Homologous chromosomes pulled apart
Telophase I
Nuclear Envelope reforms
Cytokinesis I
Cell splits into two
Prophase II
Centrioles divide and move to opposite poles
Metaphase II
Chromosomes attach to spindle fibres and line up along equator
Anaphase II
Sister chromatids break apart at centromere and migrate to opposite poles
Telophase II
Nuclei reform, Chromosomes uncoil
Meiosis is a double division and the terminology makes describing the process tricky. Make sure you know when the sister chromatids are separated (anaphase II) and when homologous chromosomes are separated (anaphase I). NOTE - no DNA replication betw

Summary of Meiosis

Cell Division Resources

Cell Division
Cell Division

This fantastic App is used by all of my students. It includes a glossary and a series of diagrams explaining the stages of BOTH mitosis and meiosis. A fantastic revision resource.

All About Mitosis and Meiosis: Life Science (Science Readers)
All About Mitosis and Meiosis: Life Science (Science Readers)

If you are feeling more traditional, this is a great resource comparing mitosis and meiosis. At only 30 pages, this is a great summary that goes into enough detail for college courses.


Comparison of Mitosis and Meiosis

Number of daughter cells made
Are the daughter cells identical
Number of nuclear divisions?
Haploid or Diploid?
Where does this occur?
Body Cells
Do homologous chromosomes pair up?
Growth and Asexual Reproduction
To make sex cells (gametes)
This table summarises the differences between mitosis and meiosis. KEY POINT: Remember that in mitosis, the chromosome number stays constant; in meiosis it is halved.

Crash Course in Meiosis

The above video analyses meiosis in great detail. It also has links to videos on related topics. This is a fantastic revision resource that all of my students are required to watch.

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Comments 15 comments

Robie Benve profile image

Robie Benve 3 years ago from Ohio

Great informative hub! Voted up and awesome! :)

torrilynn profile image

torrilynn 3 years ago

this will be very beneficial to me when i take Biology again

also its really does help to tell the difference between the two

thanks and Voted up

Melovy profile image

Melovy 3 years ago from UK

Congrats on your HOTD, well deserved!

Maricarmjolo profile image

Maricarmjolo 3 years ago from Jubail, Kingdom of Saudi Arabia

Very informative! Congrats! :D

rumanasaiyed profile image

rumanasaiyed 3 years ago from Sharjah, UAE

You have given very brief information.......

starbright profile image

starbright 3 years ago from Scandinavia

It's mind boggling - but a very interesting topic and one I'm sure many can benefit by. Thanks for taking the time to share. Voted up and shared.

Marcy Goodfleisch profile image

Marcy Goodfleisch 3 years ago from Planet Earth

What an amazing hub! It's like a mini chapter in biology, and excellent.presented so that it's understandable and interesting to follow! I have a question - would one of these processes be the way identical twins are created? Mitosis sounded the closest to it, to me.

Congratulations on the HOTD! Voted up and sharing!

summerberrie 3 years ago

Congrats on HOTD!

whonunuwho profile image

whonunuwho 3 years ago from United States

These key biological processes are something that all high school students should be aware of. Those who wish to go further in the science field and biological study are well benefited by this early study. Thanks for sharing this very interesting work. whonu

SidKemp profile image

SidKemp 3 years ago from Boca Raton, Florida (near Miami and Palm Beach)

This is an excellent hub. I did learn this in high school 40 years ago, and I think everyone should know it. Your presentation skills are extraordinary! I hope to come back and read about binary fission. Will you be writing about that?

rose-the planner profile image

rose-the planner 3 years ago from Toronto, Ontario-Canada

Fascinating! Excellent and insightful article. Thank you for sharing and congratulations on HOTD. (Voted Up) -Rose

Robie Benve profile image

Robie Benve 3 years ago from Ohio

Excellent hub! A well deserved HOD. Full of interesting info and great graphics.

vertualit profile image

vertualit 3 years ago from Bangladesh

Congratulations! your hub on hub of the day. Great hub. thanks for sharing...

Horatio Plot profile image

Horatio Plot 3 years ago from Bedfordshire, England.

I only read this because it was you. I was fully prepared to be bored to death, but guess what; I rather enjoyed it. You have the knack of making something dry go all moist and juicy; the sign of a great teacher and communicator. Congrats on HOTD. Hubscribers on a roll!

nicomp profile image

nicomp 17 months ago from Ohio, USA

The first instance of Mitosis and the first instance of Meiosis must have been wildly successful. They are pass-fail processes, survival-wise.

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