Chapter 18 Cell Division Lesson 3 - Stages of mitosis


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Chapter 18 Cell Division Lesson 3 - Stages of mitosis

  1. 1. Stages of Mitosis
  2. 2. I nterphase <ul><li>Is the non-dividing stage of a cell (resting stage) </li></ul><ul><li>During interphase, </li></ul><ul><li>1. Cells carry out activities like absorbing nutrients and building up protoplasm </li></ul><ul><li>2. The chromatin threads replicate , producing 2 identical chromatin threads (DNA molecules) </li></ul><ul><li>3. Centrioles divide in an animal cell </li></ul><ul><li>(Note: Centrioles are absent in plant cells) </li></ul>
  3. 3. Interphase
  4. 4. How a chromosome is formed <ul><li>Chromosomes appear as long thin threads called chromatin (chromatin threads) </li></ul><ul><li>Before cell division, </li></ul><ul><li>The chromatin threads replicate , producing 2 identical chromatin threads (DNA molecules) </li></ul><ul><li>- The 2 chromatin threads coil and shorten to become chromosomes </li></ul><ul><li>Each chromosome consists of 2 identical DNA molecules ( sister chromatids) </li></ul><ul><li>The chromatids are joined at a point ( centromere ) </li></ul>
  5. 5. How a chromosome is formed interphase prophase
  6. 6. A chromosome is formed from the condensation, coiling and shortening of chromatin threads
  7. 7. Structure of a chromosome - the point where the two chromatids touch, and w here the microtubules attach - one of the two identical parts of the chromosome after S phase
  8. 9. Prophase <ul><li>The nucleolus disappears </li></ul><ul><li>The nuclear envelope disappears </li></ul><ul><li>The chromatin threads condense, coil and shorten to become chromosomes </li></ul><ul><li>Asters (made up of microtubules) form around centrioles </li></ul><ul><li>The 2 pairs of centrioles move apart to opposite ends of the cell </li></ul><ul><li>A spindle forms with the spindle fibers extending from one pole to the other </li></ul>star-shaped structure formed in the cytoplasm of a cell having fibers like rays that surround the centrosome during mitosis
  9. 10. Prophase
  10. 11. Metaphase <ul><li>Chromosomes line up around the equator of the spindle </li></ul><ul><li>The centromere of each chromosome is attached to a spindle fibre </li></ul>
  11. 12. Attachment of microtubules to kinetochore - is the protein structure at the centromere of the chromosome where the spindle fibers attach during division to pull the chromosomes apart
  12. 13. Metaphase
  13. 14. Anaphase <ul><li>Each centromere splits </li></ul><ul><li>The spindle fibres pull the chromatids apart to opposite poles of the cell </li></ul><ul><li>Once the chromatids are separated, they are called daughter chromosomes </li></ul>
  14. 15. Anaphase
  15. 16. Telophase <ul><li>Spindle fibres breaks down </li></ul><ul><li>A nuclear envelope forms around the chromosomes at each pole of the cell </li></ul><ul><li>A nucleolus forms and the chromosome uncoil and lengthen to become thin chromatin threads </li></ul>
  16. 17. Telophase
  17. 18. Cytokinesis = division of the cytoplasm <ul><li>Furrows (cleavage) appear in the cytoplasm between the two nuclei </li></ul><ul><li>The furrows deepen and two identical daughter cells are produced </li></ul>
  18. 19. Test yourself 1. 2. 3. 4. 6. 7. 8. 9. ______________ Anaphase 5.