Meiosis

• Meiosis


  The process by which gametes (sperm and egg cells) are produced, resulting in cells with half the normal number of chromosomes
• Meiosis


  1. Chromosome duplication

  2. Chromosome pairs line up in the centre of the cell

  3. Chromosome pairs pulled apart into new cells

  4. Chromosomes line up again and arms pulled apart

  5. Four genetically different gametes produced
• Meiosis only happens in the reproductive organs (the ovaries in females and testes in males)
• Gametes only have one copy of each chromosome, so that when gamete fusion takes place, you get the right amount of chromosomes again (two copies of each)
• Cells divide by meiosis to make gametes which only have half the original number of chromosomes
• Mitosis


  1. Cell produced by gamete fusion divides to make a copy of itself

  2. Mitosis repeats many times to produce lots of new cells in an embryo

  3. Cells then start to differentiate into the different types of specialised cell that make up a whole organism
• There's loads on mitosis on page 27