Mitosis

Mitosis

1. Chromosomes

   • DNA wound tightly around proteins called histone
   • Normally unwound (Chromatin)
   • Before cell division, replicates and winds to form chromosomes (visible)
     • Twice the DNA
     • Made of two structures called CHROMATIDS held by a CENTROMERE

2. Prophase

   • Chromosomes visible as they thicken and shorten
     • Two identical chromatids
   • Animal cells: centrioles divide and move to opposite poles
     • Start to form spindle
   • Nuclear membrane disintegrates
     • Nucleolus disappears

3. Metaphase

   • Chromosomes arrange at the equator
   • Chromosomes attached to spindle by centromere

4. Anaphase

   • Spindle fibres contract
   • Centromeres split so chromatids pulled apart
   • Separate chromatids now called CHROMOSOMES
   • Very fast

5. Telophase

   • Chromosomes reach poles
   • Chromosomes uncoil and lengthen
   • Spindle breaks down
   • Nuclear membranes reforms
     • Nucleoli reappears

6. Cytokinesis

   • Centrioles divide and move to poles
   • Membrane furrows and cytoplasm splits
     • Daughter cells have all organelles needed

7. Significance

   • Growth
   • Repair damaged tissue
   • Cell replacement
   • Asexual repoduction
     • Bulbs
     • Large number of offspring for colonisation

8. Produces

   • 4 genetically identical daughter cells
     • Diploid