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1. Which of the following statements is (are) true?

2. Viruses use the host cell’s machinery to make copies of themselves. However, some human viruses need their RNA to be “transcribed” into DNA during their replication/life cycle, whereas human cells do not normally process heritable information in this direction (i.e. RNA to DNA). How could the virus replicate itself under these circumstances?

3. In 2009, an H1N1 influenza A pandemic occurred, caused by a virus that was different from the seasonal human H1N1 viruses that had been circulating among people for years. The flu was named “swine flu”, as it was thought that the virus was first transmitted from pig to human. Further examinations found various sequences from bird, pig, and human viruses within this newly identified virus. What is the most likely explanation for why this virus contained sequences from bird, pig, and human viruses?

4. Common cold is caused by many different viruses, mostly different kinds of rhinoviruses. Which of the following statements does this fact imply?

5. Picture the following scenario: A country introduces a rubella vaccination. Before this, no-one in the population had been vaccinated. From then on, 40% of all children receive a rubella vaccine at 15 months of age. Few people get vaccinated later in life. What are likely consequences? (Information: Infection with rubella confers life-long immunity.)

6. Cowpox is an infectious viral disease. The virus mainly infects rodents but also other animals including cows (the reason for its name) and humans. In humans, it leads to a rather harmless disease that resembles a mild form of smallpox, which in turn is a severe human disease with high mortality. By the second half of the 18th century, it had been realised that people who had overcome cowpox (e.g. milkmaids who had contracted the disease from cows) would not fall ill of smallpox. How can this be explained?