review+of+mitosis
TRANSCRIPT
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Review of Mitosis
Prophase
Metaphase
Anaphase
Telophase
1
2
3
4
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Overview of Mitosis: Prophase, Metaphase, Anaphase, Telophase
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Overview of Meiosis: Prophase I, Metaphase I, Anaphase I, Telophase I,
Prophase II, Metaphase II, Anaphase II, Telophase II
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Prophase I
• In prophase I:– The nuclear
membrane breaks down
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Metaphase I
• In Metaphase I:• This is different
than Metaphase in Mitosis
• Chromosomes line up in pairs
• Kinetochore fibers attach to centromeres
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One thing that happens during metaphase I is that parts of the sister chromosomes can actually cross-over and switch. This allows for new combinations of genetic material. (This is why we don’t look just like
our moms or dads) This is called genetic recombination.
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Anaphase I
• In Anaphase I– Homologous
chromosomes seperate
• The chromatids do not seperate
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Telophase I
• In Telophase I– Cells Split– New Nuclear
Membrane forms
• At this point, each cell has 46 chromosomes
• 2n
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Prophase II
• In Prophase II:
• These cells go straight from telophase I to prophase II. They skip interphase.
• NO CELL CYCLE
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Metaphase II
• In Metaphase II:– Chromosomes line
up along midline of cell
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Anaphase II
• In Anaphase II:– CHROMATIDS
separate• Just like Mitosis
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Telophase II
• In Telophase II:– Nuclear Membrane
begins to form– Each cell has 23
chromosomes– 1n
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Review of the difference between Mitosis and Meiosis
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OogenesisOogenesisOccurs in the Occurs in the ovariesovariesTwo divisions produce Two divisions produce 3 polar 3 polar
bodiesbodies that die and that die and 1 egg1 eggPolar bodies die because of Polar bodies die because of
unequal division of cytoplasmunequal division of cytoplasmImmature egg called Immature egg called oocyteoocyteStarting at puberty, one Starting at puberty, one
oocyte matures into an oocyte matures into an ovum ovum (egg)(egg) every 28 days every 28 days
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SpermatogenesisSpermatogenesis
Occurs in the Occurs in the testestestes
Two divisions Two divisions produce 4 produce 4 spermatidsspermatids
Spermatids Spermatids mature into mature into spermsperm
Men produce Men produce about about 250,000,000 250,000,000 sperm per sperm per dayday
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Questions
• What kind of cells are we creating during meiosis?
• How many chromosomes do they end up with?
• How many chromosomes do cells end with in mitosis?