8-2 Gene expression

Question 1

What are the two types of tumours?

Answer 1

• Benign
  o Grow slowly
  o Don’t spread
• Malignant
  o Grow rapidly
  o Spread to neighbouring cells via metastasis.

Question 2

What play important roles in cancer?

Answer 2

• Proto-oncogenes
  o Stimulate cells to divide by producing proteins that stimulate cell division, allow the checkpoints of the cell cycle to be passed, and can cause cancer if mutated.
• Oncogenes
  o These are formed from mutated proto-oncogenes and as a result are permanently switched on resulting in cell division that is uncontrolled.
  o It does this by permanently activating a cell surface receptor or coding for a growth factor.
• Tumour suppressor genes
  o Control cell division, cause the cell cycle to stop when damage is detected.
  o They also play a role in the programming of apoptosis.
  o When these are switched off the cell cycle becomes unregulated.
• Abnormal methylation of tumour suppressor genes and oncogenes.
  o Increased methylation also called hyper-methylation plays an important role in controlling tumour suppressor genes and oncogenes.
  o The hyper-methylation of a tumour suppressor gene called BRAC1 can lead to breast cancer.
• Increased oestrogen concentration
  o Can be linked to cancer development.
  o These elevated levels are found in fatty tissues called adipose tissue in the breast of post-menopausal women.
  o Oestrogen binds to the transcription factor which activates the genes promoting cell division, leading to tumour formation.