Meiosis and fertilisation

• Meiosis


  • Only takes place in reproductive organs
  • In humans it is testes and ovaries
• First stage of meiosis

  1. All chromosomes (in pairs) are copied

  2. Cell divides into two

  3. Cell divides one more time to form gametes

  4. Gametes have single chromosomes
• Meiosis


  • Halves the number of chromosomes
  • Produces four gametes from one original cell
  • Gametes are genetically different to each other and contain different alleles
• Sexual reproduction


  1. Male and female gametes join together (fertilisation)

  2. Restores the full number of chromosomes
• After fertilisation


  1. New cell divides by mitosis to produce identical cells

  2. Produces an embryo
• Embryo development


  • Cells differentiate to form different cell types