Intro to Meiosis

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Intro to Meiosis
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Meiosis
What is it? Who does it? Where does it happen?
Why does it happen? Why is a different
process needed?
Making sex cells (sperm eggs)
All sexually reproducing organisms
In males- in the testes In females- in the ovaries
To allow organisms to reproduce

1. Chromosome needs to be cut in half
2. Creates genetic diversity (can help evolution of
   species)

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Meiosis allows sex cells to join to form a
complete set of chromosomes/instructions to make
a new organism.
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Remember, humans have 23 pairs of chromosomes
Pairs 1-22 are said to be Homologous
chromosomes (they go together because they have
same traits but are not identical)
Gene for eye color
Gene for hair color
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Now lets look at how sex cells are made
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• Eight Stages of Meiosis
• Prophase I
• Metaphase I
• Anaphase I
• Telophase I
• Prophase II
• Metaphase II
• Anaphase II
• Telophase II

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Prophase I Crossing over occurs between
replicated homologous
chromosomes
Crossing over (exchanging parts)
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Note chromosomes in daughter cells are all
different
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Metaphase I Replicated chromosomes get next to
each other in the cell
Note Xs are next to each other,
not above each other
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Anaphase I homologous chromosomes separate
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Telophase I replicated chromosomes still need
to be separated
still looks like an X
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Now Meiosis II occurs (looks like
mitosis)
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Meiosis
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Meiosis animation
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And now lets see a more technical version
Meiosis technical
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One final detail
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The End!