cell cycle

• the process that all body cells in multicellular organisms use to grow and divide
• consists of a period of cell growth and DNA replication called interphase and a period of cell division called M phase
• M phase involves mitosis and cytokinesis
• interphase is subdivided into three separate growth stages. G1, S and G2
• its regulated by checkpoints which occur at key points during the cycle to make sure its okay for the process to continue
• G1 phase where the cell grows and new organelle and proteins are made
• G1 checkpoint is where the cell checks that the chemicals needed for replication are present and for any damage to the DNA before entering S-phase
• synthesis is when the cell replicates its DNA, ready to divide by mitosis
• G2 phase is when the cell keeps growing and proteins needed for cell division are made
• G2 checkpoint is when the cell checks wether all the DNA has been replicated without any damage. if it has the cell can enter mitosis
• diagram

  A) cell growth

  B) G0

  C) G1

  D) DNA replication

  E) S

  F) G2

  G) preparation for Mitosis

  H) Cytokinesis

  I) Telophase

  J) Anaphase

  K) Metaphase

  L) Interphase

  M) Prophase

  N) Mitosis

  O) Cell division

  
• the checkpoint in the mitosis phase checks:

  • the chromosomes are lined up correctly and all attached to the spindle fibres correctly if not they won be separated correctly
• apoptosis 


  ensures that imparable cells won't divide
• if the cells don't reach the requirements for the checkpoints it will fix itself if possible or if it can't apoptosis happens
• • proteins regulate the cell cycle
  • some are positive regulators which move the cell cycle forward
  • negative regulators move the cycle back
  • the rise and fall of different proteins show the cell when to move onto the next phase
• some cells don't go through the cell cycle so don't replicate and go into the G0 stage