Cell division and stem cells

• Stem cell


  An undifferentiated cell that can develop into one or more types of specialised cell
• Types of stem cells in mammals

  • Adult stem cells
  • Embryonic stem cells
• Adult stem cells


  • Can only differentiate to form certain types of specialised cells
  • Found in parts of the body like bone marrow
• Embryonic stem cells


  • Can differentiate into any specialised cell
  • Found in early human embryos (usually from spare embryos from fertility clinics)
• Therapeutic cloning


  Patient's cells are used to create an early embryo clone of themselves - stem cells from the embryo can then be used to treat the patient's medical conditions
• Plant meristems


  Areas where rapid cell division occurs in the tips of roots and shoots
• Cell division by mitosis

  Body cells divide to form two identical daughter cells
• First stage of cell cycle

  Cell grows bigger, chromosomes duplicate, number of sub-cellular structures (e.g., ribosomes and mitochondria) increase
• Mitosis


  1. One set of chromosomes is pulled to each end of the cell and the nucleus divides

  2. The cytoplasm and cell membrane divide, forming two identical daughter cells
• Third stage of cell cycle

  The cytoplasm and cell membrane divide, forming two identical daughter cells