Damage and disease

• what is the length of the cell cycle controlled by?

  its controlled by genes which ensure that mitosis happens where and when its needed - this allows for the timely replacement of cells and repair of tissues in adults and for correct development in embryos
• what is an advantage of the length of the cell cycle being controlled by genes?

  • it ensures that mitosis happens when and where its needed
  • this allows for the timely replacement of cells and repair of tissues in adults an for correct development in embryos
• what happens if the genes that control the cell cycle are damaged?

  if the genes that control the cell cycle are damaged, cells may fail to divide, may divide to frequently or at the wrong time - can cause cancer
• what can affect the timing of the cell cycle?

  radiation, certain chemicals and some viruses can mutate DNA, and DNA sequencing has identified specific gene mutations that affect the timing of the cell cycle
• how do genes control the cell cycle?

  genes control the cell cycle by acting as brake, preventing the cell cycle from repeating continually - these genes are called ‘tumour suppressor genes’ because they prevent rapid replication, which would lead to tumour formation
• why are the genes that control the cell cycle called the ‘tumour suppressor genes’?

  as they prevent rapid replication, which would lead to tumour formation
• what would happen if the ‘tumour suppressor genes’ are mutated?

  the brake is damaged and the cell may go immediately from one round of mitosis to the next and cells will replicate too fast
• what would happens if the ‘tumour suppressor genes’ mutated in solid tissue (e.g. in the wall of the colon)?

  a tumour would form
• what would happen if the ‘tumour suppressor genes’ mutated in bone marrow?

  so many immature blood cells accumulate that they spill out into the general circulation as blood cancers, such as leukaemia
• how can some genes have the potential to cause cancer?

  if they become mutated or the cell is infected with a virus
• what are genes called before they are altered, when they don’t cause cancer?

  proto-oncogenes
• what are genes called once they are altered and are able to cause cancer?

  oncogenes
• what does the chemical, doxorubicin, do to the cell cycle?

  it targets enzymes essential for the cell cycle to proceed
• what do the chemicals, vinblastine and vincristine, do to the cell cycle?

  they prevent spindle formation
• what is a proto-oncogene?

  a gene which, when mutated, becomes an oncogene and contributes to the development of cancer
• what is an oncogene?

  a gene which causes uncontrolled cell division (cancer)
• what is cancer caused by?

  • they are the result of uncontrolled cell division
  • cancerous cells divide repeatedly, out of control, with the formation of a tumour, which is an irregular mass of cells
  • cancers are sometimes initiated when changes occur in the genes that control cell division