Two groups of people had previously recovered from infection by the same form of a pathogen. One year later, group U became infected with form U of the pathogen and group V became infected with form V.
One form had the same surface antigens as the earlier pathogen. The other form had changed surface antigens.
The table shows the mean number of pathogen particles in the blood of each group.
| Day after infection | Form U particles per mm3 ^3\,3 of blood | Form V particles per mm3 ^3\,3 of blood |
|---|---|---|
| 0 | 2000 | 2000 |
| 2 | 300 | 6000 |
| 4 | 40 | 9000 |
| 6 | 10 | 2500 |
Describe the changes in the mean number of pathogen particles in the two groups during the six days. Use information from the table.
Explain which form of the pathogen had changed surface antigens. Use information from the table.
87 exam-style questions on Edexcel GCSE Biology 5.3 Immune system and medicines, covering 5.3.1 The specific immune system, 5.3.2 Response to immunisation, 5.3.3 Advantages and disadvantages of immunisation, 5.3.4 Antibiotics and bacterial infections, 5.3.5 Aseptic techniques in culturing, 5.3.6 Cross-sectional areas of cultures, 5.3.7 Stages of developing new medicines, and 5.3.8 Production of monoclonal antibodies. Each one has a worked solution and a mark scheme showing where the marks go.