cell cycle

• the cell cycle has 3 phases

  • interphase
  • mitosis
  • cytokinesis

  
• the movement from one phase to another is triggered by chemical signals called cyclins
• interphase: cell increases in mass and size and carries out its normal cellular functions (e.g synthesising proteins and replicating its DNA ready for mitosis)
• interphase

  • G1 phase, a signal is recieved telling the cell to divide again, cells make the RNA, enzymes and other proteins required for growth
  • S phase, DNA in the nucleus replicates (resulting in each chromosome consisting of 2 identical sister chromatids)
  • G2 phase, cell continues to grow and the new DNA that has been synthesised is checked and any errors are usually repaired, other preparations for cell division are made e.g production of tubulin protein, used for microtubules for mitotic spindle
• mitosis

  follows interphase

  M phase

  cell growth stops during the M phase
• cytokinesis

  follows M phase

  • once the nucleus has divided into 2 genetically identical nuclei, the whole cell divides and one nucleus moves into each cell to create two genetically identical daughter cells
  • in animal cells, cytokinesis involves constriction of the cytoplasm between the two nuclei and in plant cells a new cell wall is formed