5.1 Mitosis


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Nuclear division. Consist of 4 phases:
Prophase, Metaphase, Anaphase, Telophase

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5.1 Mitosis

  2. 3. Significance of mitosis <ul><li>Growth- allows a zygote to produce more cell in order to grow </li></ul><ul><li>Repair and replacement- allow the multicellular organism maintain its tissues, example skin cells and blood </li></ul><ul><li>Asexual reproduction- clone </li></ul>
  3. 4. <ul><li>Somatic cells have 2 sets of chromosomes: contains a diploid number of chromosomes (2n). </li></ul><ul><ul><li>1 set inherited from each parent </li></ul></ul><ul><li>Human : have 23 pairs of chromosome. </li></ul><ul><ul><li>2n = 46 </li></ul></ul>Homologous chromosomes
  4. 5. Cell Cycle <ul><li>Cell cycle - The period that extends from the time a new cell is produced until the time the cell completes a cell division. </li></ul><ul><li>Mitosis : nuclear division </li></ul><ul><li>Cytokinesis : cytoplasmic division </li></ul><ul><li>The cell cycle is divided into two major phases: </li></ul><ul><ul><li>Interphase </li></ul></ul><ul><ul><li>Mitosis </li></ul></ul>Cell grows Cell prepares to divide
  5. 6. Interphase <ul><li>The period between division, divided into 3 sub phases (G1, S and G2): </li></ul><ul><li>G 1 - cells grow rapidly and new organelle are synthesis </li></ul><ul><li>S - synthesis of DNA and chromosomes are replicated </li></ul><ul><li>G 2 - cells prepare for mitosis , synthesis protein and mitotic spindle begin to form </li></ul>
  6. 7. Mitosis <ul><li>Mitosis is a division of the nucleus to produce two new daughter cells containing chromosomes identical to the parent cell. </li></ul><ul><li>Mitosis is a continuous process and divided into 4 main phases based on the appearance and behavior of the chromosomes. </li></ul><ul><ul><li>Prophase, P </li></ul></ul><ul><ul><li>Metaphase, M </li></ul></ul><ul><ul><li>Anaphase, A </li></ul></ul><ul><ul><li>Telophase, T </li></ul></ul>
  7. 11. Prophase <ul><li>Early prophase </li></ul><ul><li>Chromosome condense and appear shorter and thicker and become visible in a light microscope </li></ul><ul><li>Each chromosome now consists of a pair of sister chromatids joined together at centromere . </li></ul><ul><li>Nucleolus disappears & nuclear membrane disintegrates. </li></ul><ul><li>Paired centrioles move to opposite ends of the cell </li></ul><ul><li>Late prophase </li></ul><ul><li>Nuclear membrane disappears </li></ul><ul><li>Spindle form </li></ul>Centrioles Centromere
  8. 12. Metaphase <ul><li>Spindle fibres are fully form </li></ul><ul><li>Sister cromatids line up at the spindle equator/ metaphase plate. </li></ul><ul><li>Two sister chromatids are still attached to one another at the centromere. </li></ul><ul><li>At the end of metaphase, the centromers divide. </li></ul>
  9. 13. Anaphase <ul><li>Anaphase begin with the separation of the centromers </li></ul><ul><li>The sister cromatids are drawn to opposite poles of the cell by shortening of spindle fibres. </li></ul><ul><li>Once separated, chromatids are referred to as daughter chromosome. </li></ul><ul><li>End anaphase: the poles of the cell have complete and equivalent sets of chromosome. </li></ul>
  10. 14. Telophase <ul><li>Telophase begin when the two sets of daughter chromosomes have reached the two poles of the cell. </li></ul><ul><li>The spindle fibres disintegrate, the nuclear membrane forms around each set of daughter chromosomes and the nucleoli reappear. </li></ul><ul><li>The nucleolus also re-forms in each nucleus. </li></ul><ul><li>The chromosomes uncoil and become less visible under the light microscope. </li></ul><ul><li>Mitosis process is now completed. </li></ul>
  11. 15. Cytokinesis <ul><li> process of cytoplasmic division to form two daughter cells. </li></ul><ul><li>Different in animals and plants. </li></ul><ul><li>Animal cells , the cytoplasm contracts to pull the plasma membrane inwards, forming groove called a cleavage furrow </li></ul><ul><li>In plant cells , cytokinesis in cells is markedly different. </li></ul><ul><li>A cleavage furrow does not form. Instead, membrane-enclosed vesicle gather at a plant cell’s equator between the two nuclei. </li></ul><ul><li>Vesicle fuse to form a cell plate </li></ul>
  12. 18. The importance of controlled mitosis <ul><li>Controlled mitosis : the ability of the cell to divide at its own rate and time. </li></ul><ul><li>Crucial to normal growth, development and maintenance for the perpetuity of living things. </li></ul><ul><li>Eg: in plants  controlled mitosis occurs at shoots results in growth of plants. </li></ul><ul><li>in human  Malphigian layer of skin divides actively to replace dead and damaged cells. </li></ul>
  13. 19. The effects of uncontrolled mitosis in living things <ul><li>Mutation is the change in the DNA structure of the cell. </li></ul><ul><li>This change in the DNA corrupts the coded genetic instructions for mitosis control. </li></ul><ul><li>This leads to uncontrolled mitosis, which is the non-stop division of cells, producing a mass of new daughter cells, called tumour. </li></ul>
  14. 22. Uncontrolled mitosis
  15. 23. Causes of Cancer <ul><li>Genetic- some forms of cancer like prostate, colon, breast, skin, ovary are suspected to be inherited from the parents </li></ul><ul><li>Carcinogens- these are chemicals which affect genetic activity and cause cancer, e.g. of carcinogen a diesel exhaust, cigarette smoke, hair dyes, soot, arsenic, benzene and formaldehyde. </li></ul><ul><li>Radiation- excess exposure to x-ray, gamma-rays and ultra violet rays lead to increase cancer risk. </li></ul><ul><li>Viruses- some viruses (such as the HPV and HIV-1) cause cancer. </li></ul>
  16. 24. Application of Mitosis in Cloning <ul><li>Mitosis is used to improve the quality , to produce new species and to ensure uniformity in the traits . </li></ul><ul><li>Cloning : process of artificially creating a new individual that is genetically identical to an existing individual. </li></ul><ul><li>Technique in application of mitosis in cloning  tissue culture . </li></ul>
  17. 25. Application on mitosis in cloning Plant tissue Skin tissue
  18. 26. Your Task! <ul><li>By using your textbook or reference book, find the procedure on how to culture a plant tissue. </li></ul>