AQA GCSE Biology

Revision Notes

2.4.5 Cancer

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

Lifestyle Risk Factors & Cancer (1), downloadable IGCSE & GCSE Biology revision notes

  • 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

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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