A virus infects dividing cells in a plant root. At the start of an investigation, viral genetic material has entered 200 root cells. Each intact infected cell divides once every 24 hours.
Immediately after the measurement at 72 hours, a chemical pollutant is added to the soil. Tests show that this pollutant does not damage uninfected root cells.
| Time in hours | Conditions | Number of intact cells containing viral DNA | Estimated number of complete virus particles in the root sample |
|---|---|---|---|
| 0 | normal | 200 | 0 |
| 24 | normal | 400 | 0 |
| 48 | normal | 800 | 0 |
| 72 | normal | 1600 | 0 |
| 96 | pollutant present | 300 | 130 000 |
Explain how the results from 0 to 72 hours support the conclusion that the viral DNA followed the lysogenic pathway.
Explain how the pollutant could have caused the results at 96 hours and the likely effect on the root tissue if this process continued.
112 exam-style questions on Edexcel GCSE Biology 5.1 Health and communicable disease, covering 5.1.1 Communicable and non-communicable diseases, 5.1.2 Disease susceptibility interactions, 5.1.3 Pathogens as disease-causing organisms, 5.1.4 Common infections, 5.1.5 Spread and prevention of pathogens, 5.1.6 Lifecycle of a virus, and 5.1.7 Spread and prevention of STIs. Each one has a worked solution and a mark scheme showing where the marks go.