Cancer | Biology for Grade 10 PDF Download

Cancer: Principles

• Cells in the body divide by mitosis to produce more cells - this is essential for growth and to replace cells that are lost or damaged
  • Cells of the intestines are constantly dividing to replace those that are shed as food move through the digestive system
• Mitosis is just one part of the cell cycle which is regulated by many different genes to ensure that cells divide only when they need to and stop when required
• Cancer is caused as a result of changes in the DNA of cells that lead to uncontrolled growth and division - this can result in the formation of a tumour (a mass of cells)
  • Usually tumours form as a result of loss of control of the cell cycle
• Not all tumours are considered cancerous
• Benign tumours are growths of abnormal cells which are contained in one area, usually within a membrane
• Crucially, benign tumours do not invade other parts of the body
• Malignant tumour cells are cancers – the cells invade neighbouring tissues and spread to different parts of the body via the blood and lymphatic system where they form secondary tumours
• Malignant tumours are more likely to disrupt the functioning of the organ they originate in (as they invade healthy tissue) and the organs they spread to – this is why they are dangerous and how they lead to death

Lifestyle Risk Factors & Cancer

• Anyone, at any age, can develop cancer, but increasing age and many lifestyle factors are associated with an increased risk of having cancer
• Treatments are constantly being developed, with targeted therapies and immunotherapy helping to improve survival rates for many different types of cancer
• Scientists have identified lifestyle risk factors for various types of cancer
  
• There are also genetic risk factors for many types of cancer; inheriting faulty genes can make individuals more susceptible to developing cancer
  • Individuals with faulty mismatch repair (MMR) genes responsible for proofing DNA are more likely to develop cancers of the bowel and reproductive systems
  • Individuals with faulty BRCA genes are more likely to develop breast and ovarian cancer than individuals with functioning BRCA genes