cancer

• cancer is caused by uncontrolled cell division
• checkpoints at the start of each stage detects for damaged DNA and stops any damage entering mitosis
• carcinogenic agents - stimulate mutations in a gene which causes cancer
• Types of Carcinogenic agents:

  1. Ionising radiation
  2. viruses
  3. UV light
• control genes - control the checkpoints in the cell cycle
• mutated control genes won’t control the checkpoints properly —> damaged DNA can replicate —> cells divide uncontrollably —> cancer
• Types of control gene mutations:

  1. Oncogenes
  2. Tumour - suppressor genes
  3. Telomerase
• normal oncogene - code for proteins that stimulate the cell cycle by allowing cells to pass the checkpoints

  
  

  mutated gene - proteins made all the time —> cell cycle continues unchecked
• normal tumour-suppressor gene - codes for proteins that stop the cell cycle by blocking the checkpoints

  
  

  mutated gene - stops correct protein being formed —> cell cycle continues unchecked
• normal telomerase gene - codes for the enzyme telomerase which extends telomeres on the ends of each chromosome

  
  

  usually telomeres get shorter after every cell division —> limits cell division

  
  

  mutated gene - telomeres are replaced after each division —> no limit for cell division
• Anti - cancer drugs:

  1. drug 1 - stops DNA replication
  2. drug 2 - stops spindle fibres forming
• tumour - mass of identical cells formed from uncontrolled cell division
• Benign tumours:

  1. are encased in a capsule
  2. do not cause cancer
  3. do not invade other tissues and cause damage
  4. secondary tumours do not form = no metastasis occurs
• Malignant tumours:

  1. can cause cancer
  2. grows quickly and spreads throughout the surrounding tissue = metastasis occurs --> secondary tumours can form
• family history of cancer = cancer gene could be inherited
• more melanin content = more protection against UV radiation
• Both types of tumour may:

  1. damage the organ concerned
  2. cause blockages
  3. cause damage/exert pressure on other organs