A scientist places 10 000 identical human skin cells in each of three dishes. The dishes are exposed to the same ionising radiation source at the same distance for different times.
The scientist records the percentage of cells alive immediately after the exposure. After four weeks, the scientist counts the abnormally fast-growing cell clusters.
| Exposure time in min | Cells alive immediately after exposure in % | Number of abnormally fast-growing cell clusters after four weeks |
|---|---|---|
| 0 | 99 | 1 |
| 2 | 84 | 7 |
| 6 | 57 | 18 |
Explain how the results show that exposure to ionising radiation can have two different effects on cells and can increase the risk of a tumour.