Question 1

Which of the following best describes the initial step required for a bacteriophage to infect a bacterial cell?

Accepted Answer

The phage must bind to a specific host cell receptor on the bacterial surface.

Question 2

During the lytic cycle of bacteriophage T4, which event occurs LAST before the release of progeny phages?

Accepted Answer

Formation of new viral particles and synthesis of lysis proteins.

Question 3

A researcher observes that a bacteriophage can integrate its genome into the host DNA and remain dormant. What is the term for this type of phage?

Accepted Answer

Temperate phage

Question 4

Which of the following best explains why bacteriophages cannot infect human cells?

Accepted Answer

Human cells lack the specific cell surface receptors required for phage attachment.

Question 5

What is the primary function of the tail fibers in bacteriophage T4?

Accepted Answer

To bind to the host cell receptor, specifically the OmpC porin.

Question 6

Which replication mechanism is shared by both T4 and lambda (λ) phages and results in the formation of concatemers?

Accepted Answer

Rolling circle replication

Question 7

A student is culturing bacteriophage on E. coli using the plaque assay method. If 100 plaques are observed on a plate after serial dilution, what does this indicate?

Accepted Answer

100 phage particles infected and lysed E. coli cells, each plaque representing a plaque forming unit (pfu).

Question 8

Which of the following environmental cues is most likely to trigger the switch from lysogenic to lytic cycle in a temperate phage?

Accepted Answer

DNA damage or other events threatening host cell survival

Question 9

In the packaging of T4 phage DNA, each virion contains a genome that is slightly longer than the complete phage chromosome. What percentage of the genome size is typically packaged?

Accepted Answer

$$103\%$$

Question 10

Which process allows a bacteriophage to transfer random fragments of bacterial DNA to another bacterium during the lytic cycle?

Accepted Answer

Generalized transduction

Question 11

During lambda (λ) phage infection, what is the role of the cos sites?

Accepted Answer

They determine where the genome is cut and packaged during replication.

Question 12

Which of the following best describes the difference between the DNA structure of T4 and lambda (λ) phages upon entry into the host cell?

Accepted Answer

T4 circularizes with terminal repeats; λ circularizes via cohesive (cos) ends.

Question 13

A bacteriophage is observed to exit the host cell without causing cell lysis, allowing the host to survive but grow slowly. What is this type of release called?

Accepted Answer

Slow-release replication

Question 14

Which of the following is TRUE regarding the number of lysogenic viruses of a particular type that can be present in a host cell?

Accepted Answer

Only a single lysogenic virus of a particular type can be present in a host cell.

Question 15

Which step in the T4 phage life cycle is responsible for the arrest of host gene expression?

Accepted Answer

Early mRNA synthesis

Question 16

What is the main difference between generalized and specialized transduction?

Accepted Answer

Generalized transduction transfers random bacterial DNA fragments; specialized transduction transfers specific genes adjacent to viral attachment sites.

Question 17

If a lambda (λ) phage infects an E. coli cell and environmental conditions remain stable, what is the most likely outcome?

Accepted Answer

The phage will integrate its genome as a prophage and remain dormant (lysogeny).

Question 18

Which of the following best describes the process of 'rolling circle replication' in bacteriophage genome replication?

Accepted Answer

Continuous synthesis of multiple genome copies linked as concatemers.

Question 19

A scientist wants to calculate the multiplicity of infection (MOI) for a phage culture. If 1 x $$10^6 E. $$coli cells are mixed with 1 x $$10^5$$ phage particles, what is the MOI?

Accepted Answer

$$MOI = \frac{1 	imes 10^5$}{1 	imes 10^6$} = 0.1$$

Question 20

Which of the following is a correct sequence of events in the lytic cycle of T4 phage infection?

Accepted Answer

Adsorption → Early mRNA synthesis → DNA replication → Late mRNA synthesis → Host cell lysis

Bacteriophages: Structure, Life Cycles, and Applications

Guida di studio - Domande di pratica

Study guide - Flashcard