Meiosis and Mitosis

• Sexual Reproduction


  Genetic information from two organisms (a father and a mother) is combined to produce offspring which are genetically different to either parent
• Sexual Reproduction


  1. Mother and father produce gametes

  2. Gametes are sperm cells and egg cells

  3. Gametes are haploid (half the number of chromosomes)

  4. Fertilisation - male gamete fuses with female gamete to form zygote

  5. Zygote undergoes cell division (mitosis) and develops into an embryo
• Offspring inherit features from both parents - it's received a mixture of chromosomes from its mum and its dad
• Fertilisation of gametes is random, producing genetic variation in the offspring
• Meiosis


  Type of cell division that produces genetically different cells, unlike mitosis
• Meiosis


  1. Cell duplicates its DNA

  2. Chromosomes line up in pairs in the centre

  3. Pairs are pulled apart, each new cell gets one copy of each chromosome

  4. Second division - chromosomes line up again, arms are pulled apart

  5. Results in 4 genetically different haploid gametes
• In humans, meiosis only occurs in the reproductive organs (ovaries and testes)
• Asexual Reproduction


  A way an organism can reproduce on its own
• Mitosis


  One of the two ways a cell can divide
• Mitosis


  1. DNA duplicates

  2. DNA forms X-shaped chromosomes

  3. Chromosomes line up at the centre of the cell

  4. Cell fibres pull the chromosomes apart

  5. Membranes form around each set of chromosomes

  6. Cytoplasm divides
• Mitosis


  • Produces genetically identical cells
  • Used for growth and repair in plants and animals
  • Used in cloning
• Asexual reproduction


  Involves mitosis
• Asexual reproduction


  • Only one parent involved
  • Offspring are genetically identical to the parent