Cell Division and Mitosis

1. Cell Division and Mitosis TB 174-180

2. What you will learn: • EXPLAIN why mitosis is important. • EXAMINE the steps of mitosis. • COMPARE mitosis in plant and animal cells. • LIST two examples of asexual reproduction

3. Why this is IMPORTANT • Your growth, like that of many organisms, depends on cell division

4. I. Why is cell division important? • Many organisms begin as one cell • Cell-division increases the total amount of cells in an organism • Even after growth stops, the body still needs cell division. Ex: red blood cells • Single-celled organisms use cell division to reproduce themselves

5. II. The Cell Cycle • Life Cycle begins with formation, followed by growth and development, and ends with death. • Length of Cycle (Fig. 2 pg.175) • Series of events that takes place from one cell division to the next • Time of life cycle varies with different cells • Cells in humans that are needed for repair, growth, or replacement constantly repeat the cycle

6. II. The Cell Cycle B. Interphase- period of cell growth and development • Eukaryotic cell (cell with a nucleus)- spends most of cell cycle in Interphase • Cells in the body that no longer divide (nerve/muscle) are always in Interphase • Actively dividing cells copy hereditary material and prepares for division during Interphase • DNA replication (copying) occurs during Interphase WHY is it important to copy hereditary material? • Before dividing, a copy of hereditary material MUST be made so new cells will have a copy • Cells need the hereditary material to carry out life functions. • After interphase, cell division begins • Cell Cycle: https://www.youtube.com/watch?v=t2kBi1OWJdc

7. III. Mitosis and Cell Division • Process in which the nucleus divides to form 2 identical nuclei • Mitosis- series of steps • Prophase • Metaphase • Anaphase • Telophase

8. 4 phases of nuclear division (mitosis), directed by the cell’s DNA (PMAT) Prophase Metaphase (Middle) Anaphase—(Apart) Anaphase—(Apart) Telophase—(Two)

9. III. Mitosis and Cell Division A. Steps of Mitosis • Chromosome- Structure in nucleus that contains heredity material • During Interphase, each chromosome duplicates • When nucleus is ready to divide, each duplicated chromosome coils tightly into 2 thickened, identical strands = Chromatids

10. III. Mitosis and Cell Division • Steps of Mitosis • 1st Phase-Prophase • Nucleolus and nucleus membrane disintegrate • Centrioles (2 small structures)- move to opposite ends of cell • Between Centrioles, threadlike spindle fibers begin to stretch across the cell ** Plant cells form spindle fibers , but not Centrioles

11. Prophase • Chromosomes coil up • Nuclear envelope disappears • Spindle fibersform

12. III. Mitosis and Cell Division • Steps of Mitosis • 2nd Phase- Metaphase • Pairs of chromatids line up across center of cell • Centromere of each pair usually attaches to 2 spindle fibers- one from each side of cell

13. Metaphase—(Middle) • Chromosomes line up in middle of cell • Spindle fibers connect to chromosomes

14. III. Mitosis and Cell Division • Steps of Mitosis • 3rd Phase- Anaphase • Each Centromere divides and the spindle fibers shorten • Each pair of chromatids separate, and chromatids move to opposite ends of cell • Separated chromatids are now chromosomes

15. Anaphase—(Apart) • Chromosome copies divide • Spindle fibers pull chromosomes to opposite poles

16. III. Mitosis and Cell Division • Steps of Mitosis • 3rd Phase- Telophase • Spindle fibers start to disappear • Chromosomes start to uncoil • 2 nuclei form • Cytoplasm begins to separate

17. Telophase—(Two) • Chromosomes uncoil • Nuclear envelopes form • 2 new nuclei are formed • Spindle fibers disappear

18. III. Mitosis and Cell Division • Cytokinesis— the division of the rest of the cell (cytoplasm and organelles) after the nucleus divides • In animal cells the cytoplasmpinches in • In plant cells a cell plate forms • After mitosis and cytokinesis, the cell returns to Interphase to continue to grow and perform regular cell activities (Figure 5 pg. 177)

19. III. Mitosis and Cell Division • MITOSIS- https://www.youtube.com/watch?v=C6hn3sA0ip0 • MITOSIS Song- https://www.youtube.com/watch?v=I5uFuvkN97I

20. III. Mitosis and Cell Division B. Results of Mitosis and Cell Division • Mitosis = the division of a nucleus • 2 nuclei are identical to each other and to the original • Each new nucleus has the same number and type of chromosomes • The original cell no longer exists • Cell Division – replaces worn out or damaged cells

21. Cell Division Control • DNA controls all cell activities including cell division • Some cells lose their ability to control their rate of cell division – the DNA of these cells has become damaged or changed (mutated) • These super-dividing cells form masses called tumors

22. Benign tumors are not cancerous – these cells do not spread to other parts of the body • Malignant tumors are cancerous – these cells break loose and can invade and destroy healthy tissue in other parts of the body (called metastasis)

23. DNA replication, cell grows and replicates organelles DNA copies itself; chromatin Nuclear envelope disappears, spindle fibers form Chromosomes coil up Chromosomes line up in the middle Spindle fibers connect to chromosomes Spindle fibers pull chromosome copies apart to opposite poles Chromosome copies divide and move apart Nuclear envelopes reform, 2 new nuclei are formed, spindle fibers disappear Chromosomes uncoil back into chromatin Division of the rest of the cell: cytoplasm and organelles Chromatin

24. IV. Asexual Reproduction • 2 Types of Reproduction • Sexual – Requires 2 organisms – hereditary material taken from both parents • Asexual – Requires 1 parent organism • Asexual Reproduction = offspring produced will have hereditary material identical to parent organism • Cellular Asexual Reproduction • Organisms with Eukaryotic cells reproduce by mitosis and cell division

25. IV. Asexual Reproduction • Cellular Asexual Reproduction • Types of Asexual Reproduction • Vegetative Propagation • Occurs in plants • Part of plant becomes separated from the parent plant and divides by mitosis • Stem = Runner – horizontal, running over soil surface EX: Strawberry Plants

26. IV. Asexual Reproduction • Cellular Asexual Reproduction • Types of Asexual Reproduction 2. Fission • Bacterium does NOT have nucleus – Can’t use Mitosis • 1-celled bacterium without nucleus copies genetic material and divides into 2 identical organisms • https://www.youtube.com/watch?v=DY9DNWcqxI4

27. IV. Asexual Reproduction • Cellular Asexual Reproduction • Types of Asexual Reproduction 3. Budding- Figure 8A pg. 180 • New organism grows from the body of the parent organism • Ex: Hydra • Sometimes the bud on parent organism grows large enough, and breaks away to live on its own • Others like sea coral grow and stay on the parent • https://www.youtube.com/watch?v=a5oHMjGqjyo

28. IV. Asexual Reproduction • Cellular Asexual Reproduction • Types of Asexual Reproduction 4. Regeneration- • Process using mitosis and cell division to regrow body parts • Figure 8B pg. 180 • If organism breaks into pieces, whole new organisms can grow from each piece • Ex. Sponges and Sea Stars • http://www.brainpop.com/science/cellularlifeandgenetics/asexualreproduction/preview.weml