Biology B2 - cell division

• Stem cells


  • Cells that are able to divide
  • Undifferentiated (not specialised)
  • Can become other types of cells
• Pros of using embryonic stem cells


  • Can grow into any type of tissue = treat variety of diseases
  • Large numbers can be grown
  • Can be used to develop new medicines
• Cons of using embryonic stem cells


  • Harm/'death' of embryo
  • Can't give consent
  • May not work
  • Risk of stem cells to differentiate into cancer cells
• Stem cells in animals


  • Differentiation at early stage of development
  • Permenant
• Stem cells in plants


  • Cells differentiate throughout life
  • Not permanent
• Process of mitosis


  1. Replication of subcellular organisms

  2. DNA replicates

  3. Nuclear membrane breaks down

  
  

  1. pairs of chromosomes divide and are pulled to opposite sides of cell

  
  

  1.Cytoplasm and cell membrane divide

  2.Two new identical cells formed
• Similarities between mitosis and meiosis


  • Both DNA replicated
  • Subcellular structures increase in number
• Differences between mitosis and meiosis


  • Mitosis = 2 daughter cells, Meiosis = 4 daughter cells
  • Mitosis = 1 cell division, Meiosis = 2 cell divisions
  • Mitosis = cells with 2 of each chromosome, Meiosis = cells with 1 of each
  • Mitosis = daughter cells genetically identical (clones), Meiosis = daughter cells genetically different (unique)
• Purposes of mitosis


  • Growth - Mitosis produced new cells
  • Repair - To replace damaged or dead cells
  • Asexual reproduction - Produces offspring identical to parent
  • bacteria - binary fission, yeast - budding