Meiosis
Meiosis
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Somatic cells undergo Mitosis
Gametes or sex cells undergo meiosis,
resulting in a cell with half of the usual
number of chromosomes (compared to a
somatic cell).
So we say that meiosis results in a halving of
the chromosome number. Mitosis is just
copying the DNA exactly as it is.
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Meiosis
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One chromosome duplication
Two cellular divisions
Yield : 4 haploid cells
Mitosis
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One chromosome duplication
One cellular division
Yield : 2 diploid cells
Meiosis I
Homologous chromosomes line up at
the medial line, then separate as
whole chromosomes
The sister chromatids
Anaphase II
separate in Anaphase II.
Telophase II
Crossing Over
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Prophase I
A process, occurring during meiosis, in
which, homologous chromosomes exchange
reciprocal portions of themselves.
Similar to shuffling of a deck of cards.
Crossing Over
Independent Assortment
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The random distribution of chromosome pairs
during meiosis.
8 million different combinations of
chromosomes lining up in Metaphase I.
Meiosis generates diversity, mitosis does not
Gamete production in Humans
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Spermatogonium produce sperm
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Half of the sperm carry an X chromosome
Half of the sperm carry a Y chromosome
Sperm ‘travel light’ (Chromosomes,
mitochondria, flagella)
Oogonium
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Produce one egg, three polar bodies
All the cytoplasm is put into the egg
All oogonia are present at birth
Sperm
Asexual Reproduction
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Not all reproduction involves two reproductive
cells.
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Asexual reproduction
Vegetative reproduction
Regeneration
Self-fertilization
Hermaphrodites
Fertilization restores the diploid condition