Cancer

• When does cancer occur?


  When changes occur in the genes that control cell division, a mutation.
• What is an oncogene?


  A gene that has the potential to cause cancer.
• What are mutations?


  A mutation is a change in the DNA sequence of an organism.

  They're common events that don't lead to cancer most of the time.
• How do mutations occur?


  Mutations can result from errors in DNA replication during cell division, exposure to mutagens or a viral infection.
• What do most mutations usually result in?


  Early cell death

  Cell destroyed by the body's immune system
• What are the characteristics of a cancerous mutation? 


  The mutation that result in the generation of cancerous cells do not result in early cell death or being destroyed.

  This means that the harmful mutation occurring in the original cell can be passed on to all the cell's descendants.

  A typical tumour contains around a thousand million cancerous cells by the time it's detected.
• What are carcinogens?


  Any agents that may cause cancer, e.g. UV light, tar in tobacco smoke and X-rays. If the agent causes cancer it's described as carcinogenic.
• What are the characteristics of benign tumours?


  Tumours (such as warts) that do not spread from their original site, they don't cause cancer.
• What are the characteristics of malignant tumours


  Tumours that spread through the body, invading and destroying other tissues, they cause cancer.

  They interfere with the normal functioning of the organ/tissue in which they've started to grow.

  Cells can break off the tumour and travel through the blood to form secondary growths in other places  (metastasis).

  It can be very difficult to detect, locate and remove these.
• What gene does almost half of all people with cancer posses?


  A mutated p53 gene
• Why us there no single effective treatment for individual suffering from cancer?

  Because there are so many reasons why the control of cell divsion deteriorates.
• What drug inhibits the synthesis of DNA nucleotides in cells?


  Methotrexate
• What drug prevents the formation of the mitotic spindle?


  Vincristine and taxol
• What problems would these cancer drugs cause?


  They would stop all cells in the body from rapidly dividing, e.g. why patients hair falls out