Cell Division

• Chromosomes


  Molecules of DNA found in the nucleus of a cell, each carrying a large number of genes, typically found in pairs in body cells
• Genes


  Found in chromosomes in cell nuclei, encode different proteins
• The Cell Cycle and Mitosis

  1. Initial growth stage: extra ribosomes, mitochondria and other sub cellular structures produced, chromosomes replicated

  2. Mitosis: two sets of chromosomes pulled to opposite ends of the cell, nucleus divides

  3. Cell division: cytoplasm and cell membrane divide, resulting in two identical daughter cells
• Stem cells


  Undifferentiated cells that have not yet specialised to perform a specific function, can create more stem cells or differentiate into another type of body cell
• Sources of stem cells

  • Embryos
  • Bone marrow
  • Plant meristems
• Embryonic stem cells


  • Can differentiate into any type of cell that will make up the organism
• Bone marrow stem cells

  • Can only differentiate into blood cells, can only be used to replace dying cells or damaged tissue
• Plant meristem stem cells


  • Found in the roots and shoots, can replicate into any cell throughout the whole life of the plant, allowing them to grow for their whole lives
• Uses of stem cells

  • Replace damaged cells
  • Plant cloning
  • Therapeutic cloning
• Disadvantages of using stem cells in medical treatment

  • Viral infections
  • Ethical beliefs