Cell division (mitosis)

• Cell Division:

  • Two types: Mitosis and Meiosis
  • Mitosis: Produces 2 daughter cells identical to parent cell
  • Involved in growth and repair of the body
  • Meiosis: Produces 4 gametes (egg or sperm) with half the number of chromosomes of the parent cell
• Mitosis:

  • One cell splits in half to form 2 new cells
  • Original cell is the parent cell
  • New cells are daughter cells
• Phases in Mitosis:

  • DNA condenses into chromosomes
  • Membrane surrounding the nucleus breaks down
  • Network of fibres contract, pulling chromosomes to opposite poles
  • Daughter cells have the same genetic code as the parent cell
• Visible phases of Mitosis:

  • Light micrograph of phases of mitosis in Onion cells
• Chromosome Number:

  • Diploid number (2n): 46 chromosomes in each cell
  • 46 chromosomes come from 2 sets of 23 chromosomes from gametes from each parent
  • Haploid number (n): 23 chromosomes in each gamete
• When do cells replicate by Mitosis?

  • Abnormal or uncontrolled mitosis can lead to the growth of tumours or cancers
• Asexual Reproduction:

  • Some plants and animals use mitosis of particular cells to reproduce
  • No union of gametes
  • Parent and offspring are genetically identical
  • Examples: Hydra, grasses
• Regeneration of Body Parts:

  • Some organisms can regenerate whole body parts via mitosis