Cell division and cancer

• Cell division


  Process by which a cell divides into two or more cells
• Reasons cells need to divide

  • Growth
  • Repair
  • Reproduction in some single-celled organisms
• Mitosis


  Cell division for somatic cells
• Meiosis


  Cell division for sex cells (gametes)
• Mitosis


  1. Interphase

  2. Nuclear division (karyokinesis)

  3. Cytoplasm division (cytokinesis)
• Interphase


  Period between two consecutive cell divisions, longest cycle of cell division
• Phases of interphase


  • G1
  • S
  • G2
• Chromosomes


  • Found in the cell nucleus
  • Contain information that controls all the processes that take place in the cell, as well as the hereditary characteristics in the form of genes
  • DNA in the chromosomes carries the hereditary information
  • Each living organism has its own specific number of chromosomes, always an even number as chromosomes occur in pairs
• Chromatin network


  Long strands that chromosomes form when not dividing
• Chromosome structure


  • Made up of bead-shaped proteins (histones) with a long DNA molecule wound around it
  • Each chromosome consists of two individual threads called chromatids
  • Chromatids are held together by a structure called the Centromere
• Mitosis


  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase
• Prophase


  • Nuclear membrane and nucleolus disappear
  • Chromosomes form
  • Centrioles duplicate and move to opposite poles
  • Spindle threads form between the centrioles
• Metaphase


  • Chromosomes move to the equator of the cell and arrange themselves in a single line
• Anaphase


  • Centromeres divide in two
  • Spindle fibers contract and pull the chromatids towards the opposite ends of the cell (poles)
• Telophase


  • Daughter chromosomes arrange themselves at the poles
  • Spindle fibers disappear
  • Nuclear membrane appears around each group of chromosomes and a nucleolus forms in each cell nucleus
• Cytokinesis


  1. Division of the cytoplasm, happens after mitosis

  2. Different in plants and animals: Animals - cytoplasm constricts and divides the cells in two, Plants - cell plate forms and divides the cell in two
• Cancer


  Disease which begins in the cells, result of uncontrolled mitosis where cells continue to divide unnecessarily and have no function, forming a mass of cells called a tumour
• Tumours


  • Can be benign (encapsulated and does not penetrate the tissues) or malignant (harmful and spreads easily)
• Metastasis


  The development of secondary malignant growth at a distance from a primary site of cancer
• Possible causes of cancer

  • Smoking
  • Chemicals (e.g. asbestos)
  • Radiation (UV, X-rays, nuclear exposure)
  • Unhealthy diet/lifestyle
  • Hereditary factors
• Carcinogen


  Any agent which is cancer-causing
• Cancer treatments


  • Surgery
  • Chemotherapy
  • Radiotherapy
  • Traditional medications
• Chemotherapy


  Aggressive form of chemical drug therapy meant to destroy rapidly growing cells in the body, usually used to treat cancer as cancer cells grow and divide faster than other cells
• Radiotherapy


  Radiation therapy that kills cancer cells or slows their growth by damaging their DNA
• Oncologist


  Doctor who specializes in cancer treatment