Two samples each contain 100 bacteria. In every bacterium, viral DNA is incorporated into the host DNA. One sample is exposed to environmental stress and the other sample is not.
Both samples are incubated for the same length of time. Throughout incubation, the samples are observed with a microscope and the number of bacteria seen lysing is recorded. The bacteria are tested for viral DNA and complete virus particles. The results are shown in the table.
| Observation | No environmental stress | Environmental stress |
|---|---|---|
| number of intact bacteria at the end | 800 | 180 |
| number of bacteria recorded lysing | 0 | 620 |
| intact bacteria containing viral DNA | all | all |
| complete virus particles detected | no | yes |
Explain what the results suggest about how the viral DNA was inherited and how environmental stress affected the viral pathway.
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.