A virus infects 100 yeast cells in a culture. A chemical is added after the yeast cells have divided three times.
| Stage | Intact yeast cells | Yeast cells containing viral DNA | Complete virus particles outside the yeast cells |
|---|---|---|---|
| start | 100 | 100 | 0 |
| after three cell divisions | 800 | 800 | 0 |
| two hours after adding the chemical | 120 | 120 | 68 000 |
Explain which viral pathway occurred before the chemical was added and how the results show that the pathway changed afterwards.
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.