B2

• Cell division happens to repair or replace damaged cells
• In plants , they retain ability to differentiate, animal cells don;t
• Cell division - Stage 1 : Cell grows bigger. Replicates nucleus. Increases sub-cellular structure
• Cell division - Stage 2: One set of chromosomes is pulled to each side of the cell. Divides cell and nucleus
• Cell division - Stage 3: Cytoplasm and cell membrane divide to form 2 identical daughter cells
• Cytokineses - Physical process of cell division, where the cell divides into 2 identical daughters
• Stem cells are found in bone marrow, embryos, meristems
• • Embryonic stem cells - unspecialised and capable of differentiating into any cell type, enable the growth and development of tissues in embryos
  • Adult stem cells - can differentiate into a limited range of cell types, enable the replacement of dead or damaged cells
• • Advantages of stem cell technology:
  • Used to treat damage or disease e.g. type 1 diabetes, heart disease
  • Used to treat diseases that would otherwise be untreatable
  • Not rejected by the body
  • Do not have to be matched to the patient's tissue type
  • Can be used to grow organs for transplants
• • Disadvantages of stem cell technology:
  • May become contaminated during preparation and when transplanted transmit infections to the patient
  • Difficult to find suitable stem cell donors
  • No guarantee that treatment will work
  • Transplanted stem cells could cause tumours
  • Long term risks are unknown
  • Potential side effects