biology t3 genetics

• Sexual reproduction


  Joining of male and female gametes, each containing genetic information from the mother or father
• Gametes


  • Sperm and egg cells in animals
  • Pollen and egg cells in flowering plants
• A normal cell has 46 chromosomes, there are two sets of chromosomes (i.e. 23 pairs), one from the father and one from the mother
• Advantages of sexual reproduction


  • Produces variation in offspring
  • Decreases the chance of the whole species becoming extinct
  • Allows selective breeding
• Meiosis


  1. The cell makes copies of its chromosomes

  2. The cell divides into two cells, each with half the amount of chromosomes

  3. The cell divides again producing four cells, each with a quarter the amount of chromosomes

  4. These cells are called gametes and they are all genetically different from each other
• Gametes with 23 chromosomes join at fertilisation to produce a cell with 46 chromosomes, the normal number
• This cell divides by mitosis to produce many copies, and an embryo forms