mitosis and meiosis

• interphase

  • cell makes extra cell parts
  • copies all chromosomes
• prophase

  • spindle fibres form
  • nuclear membrane starts to disappear
• metaphase

  • chromosomes line up along the equator of the cell
• anaphase

  • chromosomes are pulled apart by the spindle fibres
• telophase

  • single chromosomes go to opposite sides of the cell
  • nucleus forms again
• cytokinesis

  • cytoplasm separates
  • cell divides into 2 daughter cells
• reasons mitosis is important:

  • growth
  • repair e.g cuts
  • asexual reproduction
• if mitosis isnt controlled it can lead to mutations and cancer
• meiosis has two rounds of division
• meosis steps:

  1. chromosomes make identical copies of themselves
  2. similar chromosomes pair up
  3. sections of DNA get swapped
  4. chromosome pairs separate (first cell division)
  5. second cell division happens
• growth

  permanent increase in size of an organism
• differentiaton

  cells become specialised to perform different functions
• elongation


  used by plants to grow
• problems using stem cells:

  • rejection - some bone marrow transplants dont work because the patients immune system destroys the stem cells
  • some stem cells become cancerous when implanted
• embryonic stem cells:

  • can differentiate into any specialised cell
  • collected from IVF
  • controversial
• adult stem cell:

  • can differentiate into only a few specialised cells
  • found in bone marrow
  • wont be rejected
  • difficult to extract
  • reduces need of organ transplants
• mitosis - 2 daughter cells, diploid, used for asexual reproduction

  meiosis - 4 daughter cells, haploid, used for sexual reproduction