Question 1

Which of the following statements best explains why antibiotics are ineffective against viral infections?

Accepted Answer

Viruses lack metabolic pathways targeted by antibiotics.

Question 2

A scientist discovers a new infectious agent that contains only RNA and no protein coat. Which type of pathogen is this most likely to be?

Accepted Answer

Viroid

Question 3

Which feature is shared by all viruses?

Accepted Answer

Presence of genetic material and a protein coat (capsid)

Question 4

The H1N1 influenza virus is named based on which viral components?

Accepted Answer

Hemagglutinin and neuraminidase surface proteins

Question 5

Which of the following best describes the lysogenic cycle of a bacteriophage?

Accepted Answer

Phage DNA integrates into the host genome and is replicated as the host cell divides.

Question 6

A patient receives a blood transfusion and later develops symptoms of a viral infection. Which point of entry did the virus most likely use?

Accepted Answer

Direct introduction into the bloodstream

Question 7

Which equation best represents the exponential increase in the number of infected cells during the lytic cycle, assuming each infected cell releases $$n$$ new viruses and each virus infects a new cell per cycle?

Accepted Answer

$$N = n^t$$

Question 8

Which of the following is a real-world example of a zoonotic virus that caused a pandemic due to mutation and cross-species transmission?

Accepted Answer

H1N1 influenza virus

Question 9

Why are viral envelopes important for some viruses in the infection process?

Accepted Answer

They help viruses fuse with host cell membranes and evade immune detection.

Question 10

Which of the following best explains why prions are difficult to destroy using conventional sterilization methods?

Accepted Answer

Prions are proteins that are resistant to heat, radiation, and chemicals.

Question 11

A plant exhibits mottled leaves and stunted growth. Laboratory analysis reveals the presence of a small, circular RNA molecule without a protein coat. What is the most likely cause?

Accepted Answer

Viroid infection

Question 12

Which process is responsible for the sudden appearance of emerging viruses such as HIV and West Nile virus?

Accepted Answer

Mutation, dissemination from isolated populations, and cross-species transmission

Question 13

Which of the following is NOT a typical route of viral entry into a host organism?

Accepted Answer

Absorption through intact skin

Question 14

Which of the following viruses is linked to the development of certain human cancers?

Accepted Answer

Human papillomavirus (HPV)

Question 15

A bacteriophage attaches to a bacterial cell and injects its DNA. What is the next step in the lytic cycle?

Accepted Answer

Degradation of host DNA and synthesis of viral genomes and proteins

Question 16

Which of the following best describes a viral reservoir?

Accepted Answer

An organism that carries a virus without symptoms and can transmit it to other species

Question 17

Which of the following is a major difference between the lytic and lysogenic cycles of bacteriophages?

Accepted Answer

Lytic cycle results in immediate cell lysis; lysogenic cycle involves integration of viral DNA and latency.

Question 18

Which of the following best explains why vaccination is effective in preventing certain viral diseases?

Accepted Answer

Vaccines stimulate the immune system to recognize and respond to viral components before exposure.

Question 19

Which of the following is true about the host range of a virus?

Accepted Answer

It is determined by the presence of specific attachment molecules (receptors) on host cells.

Question 20

Which of the following equations correctly represents the relationship between the diameter of a human red blood cell ($$d_{RBC}) $$and the diameter of a typical adenovirus ($$d_{virus}$$), given $$d_{RBC} = 10,000 nm $$and $$d_{virus} = 90 nm$$?

Accepted Answer

$$\frac{d_{RBC}}{d_{virus}} = \frac{10,000}{90} \approx 111$$

Viruses: Structure, Replication, and Impact

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