Cell Division: Mitosis and Meiosis

Updated on June 19, 2013
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
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

Stage
Main Event
Keyword
Interphase
DNA is replicated, Cell builds up energy reseves and grows.
Increase
Prophase
DNA Packaged - the chromosomes shorten and thicken
Packaging
Metaphase
Chromosomes line up in the middle of the cell
Middle
Anaphase
Chromatids break apart at the centromere and move to opposite poles
Apart
Telophase
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

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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, analogous 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

Stage
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.

 

Comparison of Mitosis and Meiosis

 
Mitosis
Meiosis
Number of daughter cells made
2
4
Are the daughter cells identical
Yes
No
Number of nuclear divisions?
1
2
Haploid or Diploid?
Diploid
Haploid
Where does this occur?
Body Cells
Gonads
Do homologous chromosomes pair up?
No
Yes
Function
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.

Questions & Answers

    Comments

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      • profile image

        Princess 

        10 days ago

        Not good

      • profile image

        Shaik Nishat 

        2 weeks ago

        Nice explanation ☺️

      • profile image

        alexbeen 

        2 weeks ago

        I've always tried to make comparison charts in everything I can, this made things so easier. I hope you could make more side by side comparisons like this http://ask4essay.com/difference-between-mitosis-an...

      • profile image

        Samreen qureshi 

        2 months ago

        Very good explanation about mitosis and meiosis .

        very well deserved

      • profile image

        Rishav kar 

        4 months ago

        actual state ments that i needed

      • profile image

        billy bob joe 

        5 months ago

        this was not what i wanted

      • profile image

        ajeet singh 

        8 months ago

        very nice explanation about this topic.

      • nicomp profile image

        nicomp really 

        3 years 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.

      • Horatio Plot profile image

        Horatio Plot 

        5 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!

      • vertualit profile image

        Abdus Salam 

        5 years ago from Bangladesh

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

      • Robie Benve profile image

        Robie Benve 

        5 years ago from Ohio

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

      • rose-the planner profile image

        rose-the planner 

        5 years ago from Toronto, Ontario-Canada

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

      • SidKemp profile image

        Sid Kemp 

        5 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?

      • whonunuwho profile image

        whonunuwho 

        5 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

      • profile image

        summerberrie 

        5 years ago

        Congrats on HOTD!

      • Marcy Goodfleisch profile image

        Marcy Goodfleisch 

        5 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!

      • starbright profile image

        Lucy Jones 

        5 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.

      • rumanasaiyed profile image

        Rumana 

        5 years ago from Sharjah, UAE

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

      • Maricarmjolo profile image

        Maricar M. Jolo 

        5 years ago from Jubail, Kingdom of Saudi Arabia

        Very informative! Congrats! :D

      • Melovy profile image

        Yvonne Spence 

        5 years ago from UK

        Congrats on your HOTD, well deserved!

      • torrilynn profile image

        torrilynn 

        5 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

      • Robie Benve profile image

        Robie Benve 

        5 years ago from Ohio

        Great informative hub! Voted up and awesome! :)

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