Question 1

Which of the following best describes the main structural difference between an enveloped and a non-enveloped virus, as shown in the first image?

Accepted Answer

Enveloped viruses have a lipid membrane derived from the host cell, while non-enveloped viruses lack this membrane.

Question 2

Based on the Baltimore classification (second image), which type of viral genome can serve directly as mRNA for translation in the host cell?

Accepted Answer

$$+ssRNA ($$positive-sense single-stranded RNA)

Question 3

A clear zone (plaque) on a bacterial lawn (third image) is evidence of which process?

Accepted Answer

Lysis of bacterial cells by bacteriophages

Question 4

Which structural feature of the T4 bacteriophage (fourth image) is responsible for injecting DNA into the host cell?

Accepted Answer

The contractile tail sheath

Question 5

During the lytic cycle of T4 phage (fifth image), which event occurs immediately after the phage DNA enters the host cell?

Accepted Answer

Transcription of early genes using host RNA polymerase

Question 6

The T4 phage genome is linear but maps as circular (seventh image). What molecular process allows this mapping?

Accepted Answer

Recombination between terminally redundant sequences

Question 7

How does the unique base 5-hydroxymethylcytosine in T4 phage DNA (ninth image) protect the phage from bacterial defenses?

Accepted Answer

It prevents cleavage by host restriction endonucleases.

Question 8

Which of the following best explains the use of the T7 RNA polymerase system in recombinant protein expression (image 14)?

Accepted Answer

T7 RNA polymerase transcribes genes under the T7 promoter, allowing high-level expression of foreign proteins in E. coli.

Question 9

In the regulation of the lambda phage life cycle (image 17), what is the role of the CI protein?

Accepted Answer

It represses the expression of lytic genes, promoting lysogeny.

Question 10

Which event triggers the switch from lysogenic to lytic cycle in lambda phage?

Accepted Answer

Damage to host DNA, such as from UV light, leading to CI protein inactivation

Question 11

What is unique about the life cycle of the M13 bacteriophage (images 19 and 20) compared to T4 and lambda phages?

Accepted Answer

M13 is extruded from the host cell without lysing it, allowing continuous phage production.

Question 12

How is 'phage display' (image 21) used in molecular biology research?

Accepted Answer

To identify protein-protein interactions by displaying peptides on the surface of phage particles

Question 13

Which of the following is a mechanism by which bacteria defend against bacteriophage infection?

Accepted Answer

CRISPR-Cas9 system that targets and cleaves phage DNA

Question 14

Which statement best describes the genome of bacteriophage T7?

Accepted Answer

It is a linear double-stranded DNA genome encoding its own DNA and RNA polymerases.

Question 15

Why are bacteriophages important tools in molecular biology and biotechnology?

Accepted Answer

They are used to move and replicate genes, and as vectors for cloning and protein expression.

Question 16

Which of the following best explains why the T4 phage genome is resistant to host restriction endonucleases?

Accepted Answer

The presence of glycosylated 5-hydroxymethylcytosine in its DNA

Question 17

Which of the following is a key difference between the lytic and lysogenic cycles of bacteriophage lambda?

Accepted Answer

The lytic cycle results in host cell lysis, while the lysogenic cycle involves integration of phage DNA into the host genome.

Question 18

Which of the following is true about viruses of Archaea?

Accepted Answer

Most known archaeal viruses have DNA genomes but are not closely related to known bacteriophages.

Viruses and Bacteriophages: Structure, Diversity, and Molecular Biology

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