Laboratory mice in which the $p53$ genes had been turned off developed tumours. When the $p53$ genes were switched back on, the tumour cells stopped dividing and died within a few days. The healthy cells in the mice were not affected. What do these observations suggest?
- A$p53$ protein speeds up the mitotic cell cycle
- B$p53$ protein causes all cells to die
- Cthe $p53$ gene acts as a tumour suppressor gene
- Dthe $p53$ gene encourages the growth of tumours