mitosis- cell division


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Biology: mitosis, a cell division process

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mitosis- cell division

  1. 1. Life sciences ( Miss Cybil N. Khumalo University of Johannesburg
  2. 2. CHROMOSOMES  Chromosomes form when the chromatin network in the nucleus of the cell, coil up, shortens and thickens.  Each organism has a specific amount of chromosomes.  All humans have 46 chromosomes.  These chromosomes are arranged in identical pairs called homologous chromosome pairs –  Therefore humans have 23 homologous pairs of chromosomes.  These chromosomes is only visible during cell division processes.  One chromosome consist of 2 chromatids and one centromere that attach the chromatids together.  Each chromatid consist of genes which in turn consist of DNA.
  3. 3. CHROMOSOME STRUCTURE X and Y chromosomes: gonosomes/sexchromosomes Colored bands represents different genes
  4. 4. THE PHASES OF THE CELL CYCLE The cell cycle includes the following phases:  Interphase (include G1- , S- [DNA synthesis] and G2 phase)  Mitosis  Cytokinesis  Growth The result is 2 identical cells.
  5. 5. Why is Mitosis important? Allow an organism to grow. Repairs damaged cells/tissue. Replace dead cells/tissue. Reproduction in some simple organisms.
  6. 6. Where does Mitosis take place?  In all somatic cells (include all body cells and excludes the sex cells – sperm/egg cells)
  8. 8. INTERPHASE  Cell builds up enough energy for division process.  DNA replication occurs  Cell look normal, like before division
  9. 9. PROPHASE  Nuclear envelope and nucleolus disappear.  Chromatin become more tightly coiled, and condenses into individual chromosomes. Chromosomes arrange randomly in the cell.  Centrioli move to opposite poles, with spindle fibers stretching between them.
  10. 10. METAPHASE  The centrioli reached the opposite poles with the spindle fibers in between.  The chromosomes arrange randomly on the equator, each single chromosome attaching to a separate spindle fiber by means of the centromere.
  11. 11. ANAPHASE  The spindle fibers pull tight.  The centromers attaching the chromatids of the chromosomes split in half.  Daughter chromosomes move to opposite poles.
  12. 12. EARLY TELOPHASE – KARYOKINESIS (DIVISION OF NUCLEUS  Daughter chromosomes reach poles.  Nuclear envelope surrounds chromosomes.  Nucleolus reappear at each pole.  Chromosomes become less condense forming chromatin.  Two identical nuclei has been formed
  13. 13. LATE TELOPHASE – CYTOKINESIS (DIVISION OF THE CYTOPLASM)  Invagination of the cytoplasm and plasma membrane occurs. (Cleavage furrow forms in animal cells and a cytoplasmic plate forms in plant cells)  Continues until the cell in divided into 2 separate cells. (Identical to one another and to the original cell)
  15. 15. CANCER  Cancer is caused by the loss of cell cycle controls in cancer cells.  Cancer cells usually continue to divide well beyond a single layer, forming a clump of overlapping cells called a tumor.  Malignant tumors invade surrounding tissues and can metastasize exporting cancer cells to other parts of the body, where they may form secondary tumors.  They do not exhibit anchorage dependence or density dependent inhibition. (information from Campbell & Reece, Biology: 2010)
  16. 16. Ovarian cancer cells Breast tumor Ovarian cancer cells dividing