4.2 Meiosis

Click here for the AHL content.

Learn.Genetics at Utah is an excellent resource for this topic, and all animations are easy enough to save.






Here’s a patient having an amnio:

Chorionic Villus Sampling:

Wellcome Trust Big Picture Magazine

Sex and Gender:


Avoiding invasive tests for Down syndrome:

This news article outlines a new blood test for Down syndrome which does not require the invasive techniques of chorionic villus sampling or amniocentesis. See if you can work through the statistics posted there:

1. What proportion of all pregnancies end up terminating due to invasive tests as a result of a ‘false-positive’ scan result?

2. Compare the proportion of women needing amniocentesis or CVS in cases where the blood test is and is not used.

3. How does the blood test work – what is being detected and how? Find out more.


This is an amazing development, and connects all aspects of the Genetics units:

  1. The links for the meiosis and karyotyping don’t seem to be working..

    But other than that, I found this page very useful! Thanks!

  2. Nicole Lawrence

    Dear Steve, I love your resources. Thank you so much for sharing. They provide me with a wonderful resource for modelling to my students how to use the internet for good – and to filter out the overwhelming amount of content that doesn’t suit IB Biology at all.
    I am planning on using your 4.2 essential biology questions for homework during this unit. Do you have an answer scheme available?

    • Hi Nicole,

      Thank-you for the kind comments! I actually don’t have an answer key for these, though they are mostly from the presentations. To be honest, I don’t use them in class any more – but leave them up for students (and teachers) who want them.

      Sorry I can’t be of more help,


  3. Nicole Lawrence

    Thanks Stephen, I think I’ll task this to the students on a rotation basis. Thanks for leaving them there. I find they’re wonderful background work to have the students to supplement what we do in class!

  4. Reloaded beats (Tripolar)

    Hi Stephen,

    I’m 14 years old IB student from Seville and I have to congrat-you because your resources are amazing! Thank you so much for sharing it!

    Do you know that we use your resources everytime in class? Our teacher (Aureliano) has translated our presentations, and we also have got a “digital notebook”, like your students.

    It’s incredible how IB unify the classes all over the world…

    Thank you so much for sharing this amazing resources!

    • Hi! Thanks for the kind comments. I think it’s awesome that your teacher has taken the time to translate all of these resources – it must have been a lot of work! I would love to see where they are posted, so that I can share them with others.

      Good luck!


  1. Pingback: Ms. Westall's Classroom Website » Blog Archive » Meiosis – 10.1.3

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