Question 1

Which of the following best describes a virion?

Accepted Answer

A fully assembled virus particle capable of infecting a host cell.

Question 2

Viruses differ from bacteria in several ways. Which statement correctly identifies a key difference?

Accepted Answer

Viruses lack cellular structures such as ribosomes, while bacteria possess them.

Question 3

A virus's host range is primarily determined by:

Accepted Answer

The presence of specific receptors on the host cell surface.

Question 4

Why must viruses be grown in living cells for culturing?

Accepted Answer

Viruses require host cell machinery for replication because they lack metabolic enzymes.

Question 5

Which method is commonly used to identify viruses in clinical samples?

Accepted Answer

Polymerase chain reaction (PCR).

Question 6

Compare the lytic and lysogenic cycles: Which statement is true?

Accepted Answer

The lytic cycle results in immediate destruction of the host cell, while the lysogenic cycle allows viral DNA to integrate and persist in the host genome.

Question 7

How does lysogeny influence the evolution of bacteria?

Accepted Answer

It enables horizontal gene transfer, allowing bacteria to gain new properties such as toxin production.

Question 8

Which of the following is a characteristic unique to prions?

Accepted Answer

They are infectious proteins lacking nucleic acids.

Question 9

A patient is diagnosed with a viral infection. The virus is found to have RNA as its genetic material. Which of the following is true about RNA viruses compared to DNA viruses?

Accepted Answer

RNA viruses typically mutate more rapidly due to lack of proofreading mechanisms.

Question 10

Which of the following equations best represents the exponential increase in virion number during the lytic cycle, assuming each infected cell releases $$N$$ new virions after $$t$$ cycles?

Accepted Answer

$$V = N^t$$

Question 11

A virus is classified based on its nucleic acid type, capsid structure, and envelope presence. Which classification would best describe a virus with single-stranded RNA, icosahedral capsid, and no envelope?

Accepted Answer

Non-enveloped RNA virus with icosahedral symmetry

Question 12

A bacteriophage infects a bacterial cell and integrates its DNA into the host genome. What is the integrated viral DNA called?

Accepted Answer

Prophage

Question 13

Which of the following scenarios best illustrates the application of lysogenic conversion in medicine?

Accepted Answer

A bacterium produces a toxin only after infection by a temperate phage.

Question 14

Which of the following statements about prions is correct?

Accepted Answer

Prions are misfolded proteins that can induce misfolding in normal proteins.

Question 15

A laboratory technician is attempting to culture a virus using nutrient agar plates. The experiment fails. What is the most likely reason?

Accepted Answer

Viruses require living cells for replication and cannot grow on nutrient agar alone.

Question 16

Which of the following is NOT a characteristic of viruses?

Accepted Answer

They possess their own metabolic enzymes.

Question 17

A virus infects a cell and immediately begins producing new virions, leading to cell lysis. Which cycle is this describing?

Accepted Answer

Lytic cycle

Question 18

Which of the following best explains why prion diseases are difficult to treat?

Accepted Answer

Prions are resistant to standard sterilization methods because they lack nucleic acids.

Question 19

A virus is found to infect only human liver cells. Which factor most likely determines this specificity?

Accepted Answer

The presence of specific receptors on liver cell membranes.

Question 20

Which of the following equations represents the probability $$P of a $$virus successfully infecting a host cell, given $$n$$ available receptors and a binding affinity $$a$$?

Accepted Answer

$$P = 1 - e$$^{-a n}$$

Microbiology Study Guide: Viruses and Prions (Chapter 13)

Guida di studio - Domande di pratica

Study guide - Flashcard