Cancer (AQA GCSE Biology): Revision Note

Cancer: Principles

• Cancers can occur due to changes in the DNA of cells that lead to uncontrolled growth and division

  • The DNA changes cause mitosis to occur continuously

• Uncontrolled cell division can result in the formation of a tumour

  • A tumour is an abnormal mass of cells

• Not all tumours are considered cancerous

  • Benign tumours are growths of abnormal cells which are contained in one area, usually within a membrane

    • Benign tumours do not invade other parts of the body

  • Malignant tumour cells are cancerous

    • The cells invade neighbouring tissues and spread to different parts of the body via the blood, where they form secondary tumours

    • Malignant tumours are more likely to disrupt the function of organs; this is why they can have such serious effects on health

Lifestyle risk factors & cancer

• Some lifestyle factors are associated with an increased risk of developing cancer

• Scientists have identified lifestyle risk factors for various types of cancer, including:

  • smoking linked to lung cancer

  • exposure to ionising radiation, e.g. UV light, linked to skin cancer: the radiation causes mutations (changes in the DNA) in skin cells, which can lead to uncontrolled cell division and a tumour

  • obesity, a poor diet and high alcohol intake, linked to several cancers

  • infection with certain viruses, e.g. HPV, linked to cervical cancer

• Some cancers can also be linked to genetic risk factors