• when rate of cell multiplication is faster than the rate of cell death - casues tumour to grow. 
  • tumours often found in tissues with high mitosis rate. 
  • casued by damage to dna.
  • physical damage - uv light, asbestos 
  • chemical damage - carcinogens.
  • epigenetic damage - abnormal methylation of genes in cancer cells leads to activation or deactivation of genes whch control the cell cycle. e.g. lower levels activates genes that promote cell multipication. 

Cell Cycle:

  • proteins stimulate or prevent the next stage of the cell cycle - they activate or inhibit enymes that initiate the reactions in the next stage. 
  • cancer cells do not repsond to these proteins. 
  • oncogenes - code for proteins that stimulate transitionof next stage of cell…


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