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Mitosis

Mitosis. Unit 5. What is Mitosis?. Mitosis is the division of the nucleus This is how we get new cells from existing cells. Limits to Cell Growth. There are two reasons cells divide rather than continue to grow: The larger the cell becomes, the more demands the cell places on its DNA

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Mitosis

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  1. Mitosis Unit 5

  2. What is Mitosis? • Mitosis is the division of the nucleus • This is how we get new cells from existing cells

  3. Limits to Cell Growth • There are two reasons cells divide rather than continue to grow: • The larger the cell becomes, the more demands the cell places on its DNA • Larger cells have more trouble moving enough nutrients and wastes across the cell’s membrane

  4. 1. DNA “Overload” Cell Demands DNA Nucleus This is like a normal cell

  5. 1. DNA “Overload” Cell Demands DNA Nucleus + This is like a stressed out cell that needs to divide

  6. Exchanging Materials TOWN LIMIT (Cell membrane) This is like a normal cell

  7. Exchanging Materials TOWN LIMIT (Cell membrane) This is like a stressed out cell that needs to divide

  8. Division of the Cell • Cells divide before they get too large. • The process by which cells divide into two “daughter” cells is called cell division. This is like each new town getting it’s own “genetic library”!

  9. The Cell Cycle • During the cell cycle, a cell grows, prepares for division, and divides to form 2 daughter cells, each of which begins the cycle again. • There are 4 phases: • G1 phase • S phase • G2 phase • M phase

  10. Cell increases in size, synthesizes new proteins and organelles

  11. Chromosomes are replicated and DNA synthesis takes place

  12. Usually the shortest phase. Many of the organelles and molecules required for cell division are produced

  13. Mitosis is further divided into 4 phases and cell division occurs at the end

  14. 4 Phases of Mitosis • Prophase • Metaphase • Anaphase • Telophase

  15. Prophase • Longestpart of Mitosis (50-60% of the time) • Chromosomes become visible • Centrioles near the nuclear envelope move toward opposite poles • Condensed chromosomes become attached to spindle fibers at their centromeres • Nucleolus disappears and the nuclear envelope breaks down

  16. Metaphase • Chromosomesline up across thecenter of the cell (metaphase plate) • Microtubulesconnect the centromeres of each chromosome to the two poles of the spindle

  17. Anaphase • Centromeres split • Sister chromatids separate toward spindles on opposite sides of the cell

  18. Telophase • Once distinct chromosomes begin to disperse into a tangle of dense material • Nuclear envelope re-forms around each cluster (2) of material • Spindle breaks apart • Nucleolus visible in each daughter nucleus • Mitosis is complete

  19. End of Mitosis. What’s Next? • What we’ve got: • 2 nuclei with duplicate chromosomes in the cytoplasm of a single cell • Final task: • Divide the cytoplasm

  20. What is division of the cytoplasm called? • The division of the cytoplasm is called cytokinesis

  21. Cytokinesis • In animal cells the cell membrane draws inward and is pinched off forming two separate cells • In plants, a cell plate forms between the nuclei, turns into a separating membrane and eventually a cell wall http://www.youtube.com/watch?v=VlN7K1-9QB0 http://www.youtube.com/watch?v=s4PaOz7eWS8

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