Cell Division

• Stem cell


  An undifferentiated cell which can become any type of cell

  
• Undifferentiated


  A cell which is not yet specialised

  
• Differentiated


  A cell which is specialised to a specific function

  
• Human embryo


  A source of stem cells which can become any type of cell

  
• Bone marrow


  A source of stem cells which can become many types of cell including blood cells

  
• Meristem


  The region in plant shoots and roots where mitosis occurs and a source of stem cells in plant tissue

  
• Diabetes


  A disease of the pancreas which may be treated with stem cells

  
• Spinal cord injury


  A cause of paralysis which may be treated with stem cells

  
• Therapeutic cloning


  When an embryo is produced with the same genes as the patient as a source of stem cells

  
• Potential risks of stem cell treatment


  Viral infection, cancer and rejection unless therapeutic cloning is used
• Cloning rare plant species


  A way of protecting plant species from extinction, using meristem tissue
• Cloning disease resistant crops


  A way of providing food security, using meristem tissue
• Zygote


  A fertilised egg cell which divides to form an embryo

  
• Ethical objections


  Moral reasons people may be against stem cell treatments
• Religious objections


  Religious reasons people may be against stem cell treatments
• Advantages of bone marrow stem cells


  Can treat many blood-linked or immune-linked diseases, less ethical concerns than embryonic stem cells, bone marrow is easier to obtain than embryonic cells

  
• Advantages of embryonic stem cells


  No consent required, obtainable via embryos discarded in IVF, can be used to make any type of cell, less risk of rejection if used via therapeutic cloning

  
• Disadvantages of bone marrow stem cells


  Requires voluntary donors, bone marrow extraction can cause pain to an individual and requires consent, may have a risk of infection, can only form cells such as blood cells, risk of rejection

  
• Disadvantages of embryonic stem cells


  Ethical considerations such as potential loss of life or harm to embryo, less easily obtainable than bone marrow stem cells, risk of rejection

  
• Chromosomes


  Molecules of tightly-packed DNA that contain many genes

  
• DNA molecules


  Chemical molecules found in every living organism that hold instructions for growth and development

  
• Genetic material


  The general term for the material used to store genetic information in a cell

  
• Genes


  A small section of DNA that controls a specific characteristic

  
• Nucleus


  Contains the genetic material in a eukaryotic cell

  
• Cell cycle


  Repeating phases of cell growth, replication and division in cells

  
• Growth phase


  When the cell grows and increases its number of sub-cellular structures such as mitochondria and ribosomes

  
• Replication phase


  When the cell doubles its genetic material by synthesising new DNA

  
• Cell division


  When one cell divides to form two or more daughter cells

  
• Mitosis


  A type of cell division where two identical daughter cells are formed with the same genetic material as the parent cell

  
• Process of mitosis


  One set of chromosomes is pulled to each end of the cell, the nucleus then divides, the cytoplasm and cell membranes eventually divide, two identical cells are formed

  
• Daughter cells


  The new cells formed as a result of the division of a cell

  
• Reasons for mitosis


  Growth, repair and development of multicellular organisms
• Asexual reproduction


  How some organisms reproduce to form identical offspring using mitosis

  
• Chromosome pairs


  How chromosomes are normally found in body cells

  
• Body cell


  A typical cell that undergoes mitosis and is not involved in sexual reproduction