Question 1

Which of the following best explains why RNA viruses, such as influenza, can rapidly evolve and evade the immune system?

Accepted Answer

RNA viruses have a high mutation rate due to error-prone replication, leading to frequent genetic changes.

Question 2

What is the role of surface proteins such as hemagglutinin (H) and neuraminidase (N) in influenza viruses?

Accepted Answer

They allow the virus to match and enter specific host cells, determining host range.

Question 3

Which process allows influenza viruses to acquire genes from multiple strains, potentially leading to new pandemics?

Accepted Answer

Viral reassortment

Question 4

Why are vaccines considered one of the greatest public health triumphs of the 20th century?

Accepted Answer

Vaccines stimulate the immune system to mount defenses against inactive versions of viruses, preventing disease spread.

Question 5

Which equation best represents the central dogma of molecular biology, and how do RNA viruses defy it?

Accepted Answer

$$DNA \rightarrow RNA \rightarrow PROTEIN$$; RNA viruses use RNA as genetic material and may bypass DNA.

Question 6

A mutation in the influenza virus occurs during replication. Which outcome is most likely if the mutation is neutral?

Accepted Answer

The mutation does not affect the virus's ability to infect or reproduce, so its frequency in the population remains unchanged.

Question 7

Which of the following scenarios best illustrates natural selection acting on viral populations?

Accepted Answer

A viral strain with a mutation that evades immune detection increases in frequency over generations.

Question 8

Why is herd immunity important for protecting immune-compromised individuals?

Accepted Answer

It reduces the overall spread of the virus, protecting those who cannot be vaccinated.

Question 9

Which of the following viruses is transmitted most efficiently from person to person, based on $$R_0$$ values?

Accepted Answer

Measles ($$R_0 = 12-18$)

Question 10

Which statement best describes the genetic material of influenza viruses?

Accepted Answer

Influenza viruses have RNA as their genetic material, which can be single or double stranded.

Question 11

What is the primary reason why new strains of influenza can cause pandemics?

Accepted Answer

New strains may have surface proteins not recognized by the immune system, allowing rapid spread.

Question 12

Which of the following is a real-world example of viral reassortment leading to a new strain?

Accepted Answer

H7N9 influenza, with genes derived from four different bird strains.

Question 13

Which step in the influenza virus lifecycle is most likely to introduce genetic diversity?

Accepted Answer

Replication of the viral genome, where mutations can occur.

Question 14

Why do RNA viruses often defy the central dogma of molecular biology?

Accepted Answer

They use RNA as genetic material and may replicate or transcribe RNA directly, bypassing DNA.

Question 15

Which of the following best describes the concept of 'host range' in viruses?

Accepted Answer

The specific types of cells or organisms a virus can infect, determined by surface protein compatibility.

Question 16

A new influenza strain emerges that is not recognized by the immune system. What is the most likely evolutionary outcome?

Accepted Answer

The strain will reproduce more successfully and may dominate the population in subsequent generations.

Question 17

Which of the following is a key reason why continual monitoring of viral evolution is important for public health?

Accepted Answer

It allows scientists to detect new strains as they emerge and respond to potential pandemics.

Question 18

Which of the following is NOT a plausible outcome of a mutation in a viral genome?

Accepted Answer

The mutation always results in the virus becoming non-infectious.

Question 19

Which statement best describes how mRNA vaccines work?

Accepted Answer

They deliver mRNA encoding viral proteins, which are produced by host cells and trigger an immune response.

Question 20

Which historical influenza pandemic had the highest estimated mortality, and what was a key feature of its impact?

Accepted Answer

The 1918 (H1N1) pandemic, which killed over 50 million people, including many healthy individuals.

Viruses: Evolution, Diversity, and Public Health

Study Guide - Practice Questions