Brent Cornell

    
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

Interphase:

• 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

Prophase:

• 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

Metaphase:

• 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)

Anaphase:

• 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

Telophase:

• 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