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8.4 Meiosis and Genetic
Variation…read more

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Learning Objectives
· To learn why meiosis is necessary.
· To understand what happens during meiosis.
· To realise how meiosis creates genetic
variation.…read more

Slide 3

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Passing Information to the Next Generation
· Humans are similar because we all have the same genes.
· What gives us our quirky differences though, is the inheritance
of different alleles to those genes.
· Gametes join together at
fertilisation to form a
How you zygote.
· Gametes always have half
the normal amount of DNA
in them, compared to
You look regular body cells.
like a rat. · This is so that when two
gametes combine, the
resulting zygote contains the
correct amount of DNA.…read more

Slide 4

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Diploid and Haploid
·Normal body cells have the normal number of chromosomes
You might see this
46 explained elsewhere as `2n'.
We call these cells DIPLOID. It means that each body cell contains
two of each chromosome ­ one from mum and one from dad.
·Gametes though, have half the normal number of chromosomes
And this might be explained
as just `n'. 23
We call these cells HAPLOID. There's only one copy of each
At fertilisation, a haploid sperm will fuse with a haploid egg.... which
makes a cell with the normal, diploid number of chromosomes…read more

Slide 5

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n n
2n…read more

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Gametes are Formed by Meiosis
Meiosis is just a type of cell division. Unlike mitosis though, it's
outcome is insanely different.
Someone draw the outcome of As you can see by __________'s
mitosis here:
brilliant drawing, mitosis results in
Just like the parent cell, the daughter
cells are both diploid too.
Meiosis happens in your reproductive organs.
Ovaries if your a girl...
Testicles if you're a dude...
But how..........................................................?…read more

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