D2.1 Cell and nuclear division

• How do tumours originate?

  Control of a cell division is lost due to a mutation. The cell divides, the daughter cells inherit the loss of control, also dividing. This results in a group of cells that increasein numbers exponentially without normal control.
• What are the roles of proto-oncogenes?

  • Regulate expression of genes concerned with cell proliferation
  • Roles in secondary messenger systems that control the cell cycle
  • Concerned with growth factors or receptors for them
• Proto-oncogenes can mutate into oncogenes, which actively promote cell proliferation. Usually a mis-sense muation changes one of the amino acids in the polypeptide coded for by the gene, making it superactive.
• Tumor-suprossor genes prevent cell proliferation
• What are some other functions of tumour supressor genes?

  • Function as brakes at checkpoints in cell cycles
  • Needed for DNA repair to correct errors in replication
  • Roles in programmed cell death (apoptosis) within cells where there has been irreparable DNA damage.
• Any cell can be a tumour cell, but one mutation is usually not enough. As many as 10 mutations must be present together in a single cell for some types of tumours to form.
• Benign tumour is a tumour that tends to grow slowly and does not spread to other parts of the body
• Malignant tumour is a cancerous tumour that grows quickly and invades nearby tissues
• Primary tumour is a cancer growing at the site where the abnormal growth first occured
• Secondary tumour is formed when cancerous cells detach from the primary tumour, penetrate the walls of the lymph or blood vessels and circulate around the body, causing tumours elsewhere
• Metastasis is the movement of cells from a primary tumour to set up secondary tumours
• Primary tumour is the original tumour that has grown from a single cell.
• Secondary tumour results from the migration of cells from primary tumour to other tissues
• Malignant tumour spread to other tissues and are cancerous
• Benign tumour do not spread to other tissue and are not cancerous