5.1 mitosis


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5.1 mitosis

  2. 2. THE NECESSITY FOR THE REPRODUCTION OF NEW CELLS ORGANISMS . <ul><li>Mitosis is the process of cell division that produces two daughter cells which are genetically to each other and to their parent cell. </li></ul><ul><li>The significance of mitosis in living things: </li></ul><ul><ul><li>Repair and replace the damaged or dead cells </li></ul></ul><ul><ul><li>Increases the number of unicellular organisms. </li></ul></ul><ul><ul><li>Ensures that new cell are genetically identical to the parent </li></ul></ul><ul><ul><li>Preserve the diploid number of chromosomes </li></ul></ul><ul><ul><li>Increases the number of cells in individuals( single-celled organisms) </li></ul></ul><ul><ul><li>Aids in growth process( multi-celled organisms ) </li></ul></ul>
  3. 3. The phases in the cell cycle <ul><li>Cell cycle -the life of a cell from the time it is produced until it completely divides into two new daughter cells. </li></ul><ul><li>Activity of the cell during mitotic division: </li></ul><ul><ul><li>Preparing for the division </li></ul></ul><ul><ul><li>Produce cytoplasm and organelles-formation of daughter cells. </li></ul></ul><ul><li>Two major phases: </li></ul><ul><ul><li>Interphase </li></ul></ul><ul><ul><li>Mitotic cell division(M Phase) </li></ul></ul>
  4. 4. Phase in Cell cycle
  5. 5. Interphase PHASE DESCRIPTIONS G1(FIRST GAP) <ul><li>The size of cells increases </li></ul><ul><li>RNA is produced </li></ul><ul><li>Synthesise protein and new organelles </li></ul><ul><li>Chromosome cannot be observed clearly and known as chromatin </li></ul>S(SYNTHESIS) <ul><li>DNA synthesis </li></ul><ul><li>The DNA replication takes place </li></ul><ul><li>The copied chromosomes contain two sister chromatids which are identical </li></ul>G2(SECOND GAP) <ul><li>Cell preparing for division(mitosis) </li></ul><ul><li>The cell grows,produces organelles,protein and membrane </li></ul><ul><li>Nucleus is well-defined </li></ul><ul><li>Chromosome duplication completed </li></ul><ul><li>DNA loosely packed in long chromatin fibres </li></ul>
  6. 6. <ul><li>Interphase </li></ul><ul><li>This is the resting or non-mitotic of the cell cycle </li></ul><ul><li>It comprise G1,S and G2 stage of the cell cycle </li></ul><ul><li>DNA is replicated during the S phase of interphase </li></ul>
  7. 7. The M phase(mitosis and cytokinesis) <ul><li>PROPHASE </li></ul><ul><ul><li>If the first stage of mitosis </li></ul></ul><ul><ul><li>The chromosomes condense and become visible </li></ul></ul><ul><ul><li>The centrioles form and move toward opposite ends of the cell(the pole) </li></ul></ul><ul><ul><li>The nuclear membrane dissoves and the mitotic spindle thread is formed(from the centrioles) </li></ul></ul><ul><ul><li>Spindle fibers from each centriole attach to each sister chromatid at the kinetochore </li></ul></ul><ul><ul><li>Chromatids are connected at the centromere </li></ul></ul>
  8. 8. <ul><li>METAPHASE </li></ul><ul><li>The chromosomes lined up on the cell equator which is the metaphase plate </li></ul><ul><li>The spindle fibres are formed completely </li></ul>
  9. 9. <ul><li>ANAPHASE </li></ul><ul><li>Spindle attached to kinetochores begin to shorten </li></ul><ul><li>This exerts a force on the sister chromatids and pulls them apart </li></ul><ul><li>Spindle fibres continue to shorten,pulling chromatids to opposite poles of the cell </li></ul>Early anaphase Late anaphase
  10. 10. <ul><li>TELOPHASE </li></ul><ul><li>Both chromosomes have reached the opposite poles </li></ul><ul><li>The chromosomes decondensed </li></ul><ul><li>The nuclear enveloped is formed </li></ul><ul><li>Nucleus reformed </li></ul><ul><li>The spindle fibres dissappear </li></ul><ul><li>Once separate,the chromatds are again called chromosomes </li></ul><ul><li>Two daughter nuclei are formed with identical set of chromosomes </li></ul>
  11. 11. Cytokinesis <ul><li>Cytokinesis is the process of the cytoplasm division after the separation of chromosomes </li></ul>CYTOKINESIS IN PLANT CELL <ul><li>The vesicles move to the equator between the two nuclei and fuse to form two membranes that become cell plate </li></ul><ul><li>The cell plate grows upwards </li></ul><ul><li>The new cell wall is laid down between membranes and fuses with the existing cell wall </li></ul>
  12. 12. CYTOKINESIS IN ANIMAL CELLS <ul><li>The vesicles move to the equator between the two nuclei and fuse to form two membranes that become cell plate </li></ul><ul><li>The cell plate grows upwards </li></ul><ul><li>The news cell wall is laid down between membranes and fuses with the existing cell wall </li></ul>
  13. 13. The importance controling mitosis <ul><li>To ensure that organism can function properly </li></ul><ul><li>To ensure that organisms can grow and develop normally </li></ul><ul><li>To help in repairing damage cells and tissues for the survival of life </li></ul>
  14. 14. The effects of uncontrolled mitosis in living things <ul><li>It due to the changes of gene which control the cell cycle e,g:The growth of cancerous cell </li></ul><ul><li>Cancerous cells could lead to the death of the organism if it is not prevented from invanding and destroying neighbouring cells </li></ul><ul><li>This condition can be caused by certain virus,toxic chemical susbtances </li></ul><ul><li>The cells divide very fast and unregulated. (Tumour) </li></ul><ul><li>Benign tumour- Abnormal cells that remain at the original site and be removed by surgery </li></ul><ul><li>Malignant tumour -becomes invasive and spreads to neighbouring tissues and cells (cancer) </li></ul>
  15. 15. The application of knowledge on mitosis in cloning <ul><li>Production of genetically identical individuals </li></ul>Cloning of sheep
  16. 16. <ul><li>Producing genetically identical organisms which carry a useful gene </li></ul><ul><li>A piece of DNA carrying a gene of interest and a gene for antibiotic resistance </li></ul><ul><li>The cells is grown on a medium containing the antibiotic so that only the cells with the inserted DNA will survive </li></ul><ul><li>The nuclei from surviving cells is inserted into unnucleated egg cells </li></ul><ul><li>The egg cells is implanted into the surrogate mother </li></ul><ul><li>Clone which carry the useful gene are born </li></ul>
  17. 17. <ul><li>Application of cloning technology is important to: </li></ul><ul><li>Produce genetically identical organs for transplantation </li></ul><ul><li>Produce human tissues </li></ul><ul><li>Repopulate endangered species </li></ul>
  18. 18. The advantages and disadvantages of cloning Advantages <ul><li>Ensure the continuity of hereditary traits from the parent to the clones </li></ul><ul><li>Increase the rate of production and the quality of the products </li></ul><ul><li>Good qualities of the plants and animals can be selected and maintained in the clones </li></ul><ul><li>Many clones are produced in a short time </li></ul><ul><li>Can be carried out any time of the year </li></ul>Disadvantages <ul><li>Raise ethical issues on human The resistance of the clones towards diseases and pests is the same.If a clone is infected with a disease or attacked and die </li></ul><ul><li>Raise ethical issues on human cloning </li></ul>