Mitosis and Cancer Higher

🎓 Mitosis and Cancer Higher

The cell cycle is normally tightly controlled by a series of checkpoint proteins. Two important classes of gene are involved:

• Tumour suppressor genes (e.g., p53) produce proteins that slow down or halt cell division when DNA damage is detected. They act as the cell's "brake pedal." If these genes are mutated and stop working, cells can divide without restriction.
• Proto-oncogenes are normal genes that promote cell division. If a mutation causes them to become permanently switched on (they then become "oncogenes"), the cell divides uncontrollably.

When these control mechanisms fail, the cell enters uncontrolled mitosis — dividing continuously without the normal signals to stop. The resulting mass of cells is called a tumour. A malignant (cancerous) tumour can spread to other parts of the body through the bloodstream or lymph system, a process called metastasis.

Note: You do not need to know specific gene names for GCSE, but you should understand the principle that cancer results from mutations disrupting normal cell cycle control.