Question 1

Which of the following best describes the structure of an icosahedral virus, and which virus is a classic example of this shape?

Accepted Answer

It has a polyhedral structure with 20 triangular faces; Adenovirus is an example.

Question 2

A viral envelope is crucial for certain viruses. How is a viral envelope formed, and which of the following viruses is enveloped?

Accepted Answer

It is derived from the host cell membrane during viral budding; Influenza virus is enveloped.

Question 3

Host specificity (host range) of a virus is determined by which of the following factors?

Accepted Answer

The presence of specific receptors on the host cell surface that the virus can bind to.

Question 4

Which of the following correctly describes the lytic cycle of the T4 bacteriophage?

Accepted Answer

The virus attaches, injects DNA, replicates, assembles new phages, and lyses the host cell to release progeny.

Question 5

Lysogeny is a process in which:

Accepted Answer

A viral genome integrates into the host genome and replicates along with it without causing immediate lysis.

Question 6

Why is the viral replication cycle often considered to have only one step?

Accepted Answer

Because the burst of new virions is released at once after a latent period, rather than in multiple steps.

Question 7

Which of the following viruses is a +ssRNA virus, and what is a key feature of its replication?

Accepted Answer

Poliovirus; its RNA can serve directly as mRNA for protein synthesis.

Question 8

What is the role of reverse transcriptase in retrovirus replication?

Accepted Answer

It converts viral RNA into DNA, which can integrate into the host genome.

Question 9

Why are different techniques used to culture viruses in prokaryotic versus eukaryotic cells?

Accepted Answer

Because prokaryotic viruses (bacteriophages) are cultured using bacterial lawns, while eukaryotic viruses require tissue culture or embryonated eggs.

Question 10

Which of the following best differentiates between latent and persistent viral infections? Give an example of each.

Accepted Answer

Latent infections have periods of dormancy with no viral production (e.g., Herpes simplex); persistent infections involve continuous viral production (e.g., Hepatitis B).

Question 11

Cytopathogenic effects (CPEs) are important in diagnosing viral infections. Which of the following is an example of a CPE?

Accepted Answer

Syncytium formation (fusion of multiple host cells into a single large cell).

Question 12

According to the Protooncogene Theory, how can insertional inactivation by a virus lead to oncogenesis?

Accepted Answer

By integrating viral DNA near a protooncogene, disrupting its regulation and potentially leading to uncontrolled cell division.

Question 13

Which of the following is an example of a mutualistic symbiotic relationship?

Accepted Answer

E. coli in the human gut producing vitamin K for the host.

Question 14

A disease syndrome consists of two parts. What are they, and how are they defined?

Accepted Answer

Symptoms (subjective changes felt by the patient) and signs (objective changes observed by others).

Question 15

Which of the following best defines a nosocomial infection?

Accepted Answer

An infection acquired in a hospital or healthcare setting.

Question 16

During which period of human disease is a patient most likely to transmit the infection to others, even if symptoms are not yet present?

Accepted Answer

Incubation period.

Question 17

Which of the following best describes the difference between incidence and prevalence in epidemiology?

Accepted Answer

Incidence is the number of new cases in a specific time period; prevalence is the total number of cases (new and existing) at a given time.

Question 18

A patient develops a localized infection that later spreads to other parts of the body via the bloodstream. Which terms best describe the initial and subsequent infections?

Accepted Answer

Initial: local infection; Subsequent: systemic infection.

Question 19

Which of the following equations correctly represents the calculation of disease incidence rate in a population?

Accepted Answer

$$	ext{Incidence Rate} = \frac{	ext{Number of new cases during a specific period}}{	ext{Population at risk during the same period}} 	imes 100,000$$

Question 20

A hospital experiences an outbreak of a contagious disease. Which of the following best describes a contagious disease?

Accepted Answer

A disease that can be transmitted easily from person to person.

Exam 2 Microbiology Virus & Disease Review – Step-by-Step Study Guidance

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