Sexual and asexual reproduction and Meiosis

• Sexual reproduction

  • Fusion of male and female gametes
  • Sperm and egg cells in animals
  • Pollen and egg in plants
  • Mixing of genetic info leasing to variety in offspring
  • Meiosis is involved, leading to non-identical cells
• Asexual reproduction

  • One parent and no fusion of gametes
  • No mixing of genetic info
  • Mitosis involved, leading to genetically identical offspring or clones
• 3 Differences between cell division for sperm cells compared with cell division for liver cells

  • Meiosis for sperm cell and mitosis for liver
  • Two cell divisions to form sperm and one cell division to form liver cells
  • Sperm cells have 23 chromosomes and liver has 46
  • Four genetically different sperm cells and two genetically identical liver cells
• Mitosis and the Cell Cycle

  1. Before a cell can divide it needs to grow and increase the number of sub-cellular structures such as ribosomes and mitochondria. The DNA replicates to form two copies of each chromosome.
  2. In mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides.
  3. Finally the cytoplasm and cell membranes divide to form two identical cells.
• Meiosis - Cells dividing to form Gametes

  • Copies of the genetic information are made

  • The cell divides twice to form four gametes, each with a single set of chromosomes

  • All gametes are genetically different from each other
• Fertilisation

  • Gametes join at fertilisation to restore the normal number of chromosomes.
  • The new cell divides by mitosis.
  • The number of cells increases
  • As the embryo develops cells differentiate