Cancer

• RNA interference (RNAi)


  1. RNA molecules act to inhibit gene expression

  2. Usually by destroying mRNA so that it cannot be translated

  3. Occurs in eukaryotes & some prokaryotes
• Benign tumours


  • Slow growth
  • Don't spread easily
  • Defined by a clear boundary due to cell adhesion molecules
  • Cells retain function & normal shape
  • Easy to treat
• Malignant tumours


  • Rapid, uncontrollable growth
  • Difficult to treat
  • Ill-defined boundary (finger-like projections)
  • Cells do not retain function and often die
  • Spreads quickly and easily (metastasis)
• Tumour-suppressor genes


  • Code for proteins that control cell division; in particular, stopping the cell cycle when damage is detected
  • They are also involved in programming apoptosis i.e. 'self destruction' of the cell
• How tumour-suppressor genes can be involved in developing cancer


  1. A mutation in the gene could code for a nonfunctional protein (I.e. Gene isn't expressed)

  2. Increased methylation or decreased acetylation (of T-S gene) could prevent transcription

  3. Cells will divide uncontrollably resulting in a tumour
• Proto-oncogenes


  Control cell division; in particular, code for proteins that stimulate cell division
• How proto-oncogenes can be involved in developing cancer

  1. Mutation in the gene could turn it into a permanently activated oncogene

  2. Decreased methylation or increased acetylation can cause excess transcription

  3. Results in uncontrolled cell division & formation of a tumour
• How abnormal methylation of genes can cause cancer

  Hyper-methylation of tumour-suppressor genes or oncogenes can impair their function & cause cells to divide uncontrollably
• How oestrogen can be involved in developing breast cancer


  1. Oestrogen is an activator of RNA polymerase

  2. Therefore in areas of high oestrogen concentration, such as adipose tissue in the breasts, cell division can become uncontrollable