Cancer (Leaving Cert Biology): Revision Notes

Cancer

• Cancers can be benign or malignant.
• Benign tumour
  • Abnormal cells divide uncontrollably by mitosis to form a tumour.
  • These cells do not spread or invade other body tissues.
• Malignant tumour
  • Abnormal cells divide uncontrollably by mitosis to form a tumour.
  • These cells spread to other tissues (metastasis).
  • Malignant cancer cells can divide indefinitely, leading to further growth and spreading.

Causes of Cancer

1. Mutations

• Cancer occurs when normal genes are altered (mutated) to form cancer-causing cells.
• A mutation is any change to the structure of DNA.

2. Carcinogens

• Substances that cause cancer are called carcinogens.
• Carcinogens damage the DNA in genes. Any change to the structure of DNA is known as a mutation.
• There are specific genes that, if mutated, can lead to cancer. These genes are called oncogenes.
• Some common carcinogens include:
• Cigarette smoke
• Asbestos
• Ultraviolet (UV) radiation from the sun
• X-rays