Cell division in sexual reproduction

• Female gametes


  Made in the ovaries
• Male gametes


  Made in the testes
• Gametes


  Produced by meiosis
• The chromosome number is halved during meiosis, with one set of chromosomes inherited from the mother and the other set inherited from the father
• Cell division to form gametes


  1. Genetic information is copied

  2. Cell divides twice to form four genetically different gametes, each with a single set of chromosomes
• More variation is added during fertilisation when the single set of chromosomes from the egg and sperm combine to form a new cell with the full set of chromosomes
• In humans, the egg and sperm each have 23 chromosomes, and when they join they produce a single new body cell with 46 chromosomes
• After fertilisation


  1. The unique new cell begins to divide by mitosis to form a new individual

  2. The number of cells increases rapidly

  3. As the embryo develops, the cells differentiate to form different tissues, organs and organ systems
• Asexual reproduction


  Offspring are a product of mitosis from the parent cells, containing the same chromosomes and genes as the parent, so there is no genetic variation
• Sexual reproduction


  • Gametes are produced by meiosis in the sex organs of the parents, introducing variation as each gamete is genetically different
  • When the gametes fuse, the offspring inherits one set of chromosomes from each parent, adding more variation
  • The chromosomes will contain different forms of the same genes (alleles) from each parent, further contributing to variation