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•  Identification of phases of mitosis in cells viewed with a microscope or in a micrograph

Mitosis is the process of nuclear division, whereby duplicated DNA molecules are arranged into two separate nuclei

Mitosis is preceded by interphase and is divided into four distinct stages: prophase, metaphase, anaphase, telophase

  • The division of the cell in two (cytokinesis) occurs concurrently with the final stage of mitosis (telophase)

Before Mitosis



  • DNA is present as uncondensed chromatin (not visible under microscope)
  • DNA is contained within a clearly defined nucleus
  • Centrosomes and other organelles have been duplicated
  • Cell is enlarged in preparation for division

Stages of Mitosis



  • DNA supercoils and chromosomes condense (becoming visible under microscope)
  • Chromosomes are comprised of genetically identical sister chromatids (joined at a centromere)
  • Paired centrosomes move to the opposite poles of the cell and form microtubule spindle fibres
  • The nuclear membrane breaks down and the nucleus dissolves


  • Microtubule spindle fibres from both centrosomes connect to the centromere of each chromosome
  • Microtubule depolymerisation causes spindle fibres to shorten in length and contract
  • This causes chromosomes to align along the centre of the cell (equatorial plane or metaphase plate)


  • Continued contraction of the spindle fibres causes genetically identical sister chromatids to separate
  • Once the chromatids separate, they are each considered an individual chromosome in their own right
  • The genetically identical chromosomes move to the opposite poles of the cell


  • Once the two chromosome sets arrive at the poles, spindle fibres dissolve
  • Chromosomes decondense (no longer visible under light microscope)
  • Nuclear membranes reform around each chromosome set
  • Cytokinesis occurs concurrently, splitting the cell into two

Overview of the Process of Mitosis