Variation and Meiosis
What makes us different?
Lesson Objectives
1. Understand genetic and environmental
variation, using examples
2. Understand the processes of Crossing Over,
Independent assortments & Fertilisation
3. Know how these processes contribute to
variation in offspring.
Starter Activity
• You each have a post it note with a stage of
Meiosis written on it.
• Draw that stage on the post it.
• Stick it to the window.
Variation
• Brainstorm all the characteristics / traits that
make us different.
• These could be genetic or environmental
features.
Variation
• What is meant by Genetic Difference
(Variation)?
• http://www.youtube.com/watch?v=a5yzRRvR
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Activity.
• Complete the Variation worksheet activity in
pairs or small groups.
Crossing Over
• Write down a definition of Crossing Over from
the work we did yesterday.
• When (which stage) during Meiosis does it
happen?
• Why is it important?
Independent Assortment
• Sometimes called independent segregation or
random assortment.
• Happens in Metaphase 1 and Metaphase 2
Metaphase 1
• When chromosomes line up along the equator
with their homologous pairs, they do so
randomly.
• i.e. There is no specific order
Anaphase 1
• So, when they separate from their
homologous pair in anaphase, this is also
random.
Metaphase 2/ Anaphase 2/Telophase 2
• Again, another random order
• So, when the 4 daughter haploid cells are
formed there is a random combination
(independent assortment) of chromosomes.
• This means that there can be a lot of variation
in offspring.
Fertilisation
• How does the process of fertilisation
contribute to genetic variation?
Genetic Variation
• http://www.youtube.com/watch?v=UjMn4oHf
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