Question

1. Use the following figure and information to answer the question(s) below. 100,000 Virus A - Virus B Number Viruses 10,000 - per millilter of culture 1000 - ---- 30 60 120 Time After Infection in minutes) Cells were infected with approximately 1000 copies of either virus A or virus B at the O time point. At five-minute intervals, a sample of the virus and cell mixture was removed. The intact cells were removed from the sample, and the number of viruses per milliliter of culture was determined. Using the data in the figure above, how long does it take for virus A to go through one lytic cycle? Virus B? 2. Viruses use the host's machinery to make copies of themselves. However, some human viruses require a type of replication that humans do not normally have. For example, humans normally do not have the ability to convert RNA into DNA. How can these types of viruses infect humans, when human cells cannot perform a particular role that the virus requires?

Answer 1

1. Virus A takes about 45 minutes to go through one lytic cycle. Virus B takes about 60 minutes to go through one lytic cycle.

(This is because as the virus completes its lytic cycle in the hosts, it ruptures the host cell and comes out in the culture medium. This would lead to an increase in the number of viruses per ml of culture, shown in the graph. The highest value for this is reached in 45 and 60 minutes respectively for virus A and B.)

2. In such cases the virus packs the required proteins (like reverse transcriptase or integrase) for its replication and propagation in its capsule and infects the host cell both with its genome and the required proteins.