Question 1

Which of the following best describes a virus?

Accepted Answer

A non-cellular particle that contains a genome and is an obligate intracellular parasite

Question 2

Which type of viral genome is most commonly found among bacterial viruses?

Accepted Answer

Double-stranded DNA ($$dsDNA)$$

Question 3

During the lytic cycle of a bacteriophage, what is the correct order of the main steps?

Accepted Answer

Attachment, penetration, synthesis, assembly, release

Question 4

What is the function of the phage tail sheath during infection of a bacterial cell?

Accepted Answer

It contracts to inject the phage genome into the host cell

Question 5

Which of the following best explains why most RNA viruses have linear genomes?

Accepted Answer

RNA is structurally less stable than DNA and forms linear molecules

Question 6

A bacteriophage infects a bacterial cell and integrates its genome into the host chromosome, remaining dormant for several generations. What is this state called?

Accepted Answer

Lysogeny

Question 7

What triggers induction of a prophage from the lysogenic to the lytic cycle?

Accepted Answer

Environmental stress that threatens host cell survival, such as DNA damage

Question 8

Which of the following is a key difference between virulent (lytic) and temperate (lysogenic) phages?

Accepted Answer

Virulent phages only undergo the lytic cycle, while temperate phages can undergo both lytic and lysogenic cycles

Question 9

In a one-step growth curve experiment, what does the 'burst size' represent?

Accepted Answer

The number of virions released per infected cell

Question 10

Which bacterial defense mechanism involves the use of restriction enzymes?

Accepted Answer

Degradation of non-methylated foreign DNA

Question 11

What is the role of the CRISPR/Cas system in bacteria?

Accepted Answer

It provides adaptive immunity against phage infection by recognizing and degrading foreign DNA

Question 12

A researcher observes that after infecting E. coli with a certain phage, no infectious virions are detected for the first 20 minutes, but then a sharp increase in virion count occurs. What is the period with no detectable virions called?

Accepted Answer

Eclipse period

Question 13

Which of the following best describes the function of early genes expressed by a bacteriophage after infection?

Accepted Answer

They encode proteins that promote phage genome replication

Question 14

Why do some bacteria lose the receptor required for phage adsorption as a defense mechanism?

Accepted Answer

To prevent phage attachment and subsequent infection

Question 15

Which of the following statements about viral genomes is correct?

Accepted Answer

DNA genomes may be linear or circular, but RNA genomes are always linear

Question 16

A phage repressor protein (such as cl in lambda phage) is important because it:

Accepted Answer

Prevents expression of lytic genes, maintaining lysogeny

Question 17

Which of the following best explains why the CRISPR/Cas system is considered an adaptive immune system for bacteria?

Accepted Answer

It acquires and stores sequences from invading phages to recognize and destroy them in future infections

Question 18

If a bacteriophage has a latent period of 30 minutes and a burst size of 200, how many virions would be released from 100 infected cells after one complete cycle?

Accepted Answer

$$200 	imes 100 = 20,000$$

Question 19

Which of the following is NOT a typical way bacteria defend themselves against phage infection?

Accepted Answer

Producing enzymes that synthesize viral DNA

Question 20

A scientist is studying a new bacteriophage and observes that its genome is segmented and linear. Based on this information, which type of nucleic acid is most likely present in this phage?

Accepted Answer

RNA

Bacteriophage Biology and Infection Mechanisms

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