Bacteriophage and Its Replication Cycles

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Questions and Answers

What are the main components of a bacterial genome?

R factors, F factors, and bacterial chromosome

Only plasmids and prophage

Bacterial chromosome, plasmids, and prophage (correct)

Plasmids and DNA fragments only

Which statement accurately describes plasmids?

Plasmids are usually larger and contain more genes than the bacterial chromosome.

Plasmids can be lost spontaneously during bacterial replication. (correct)

Plasmids can be either circular or linear DNA segments.

Plasmids are essential for bacterial growth and replication.

What function do R factors serve in bacteria?

They store energy for bacterial metabolism.

They promote the formation of sex pili for reproduction.

They provide structural integrity to the bacterial cell.

They confer resistance to antibiotics and toxins. (correct)

The F factor in plasmids is primarily associated with which function?

Coding for sex pilus formation for bacterial conjugation Signup and view all the answers

Which of the following statements about plasmids is true?

Plasmids may contain genes related to adhesion and invasion. Signup and view all the answers

What shape is the head of a bacteriophage?

Hexagonal Signup and view all the answers

What occurs during the penetration stage of the lytic cycle?

The bacteriophage injects its DNA into the bacterium Signup and view all the answers

Which process describes the detachment of prophage from the bacterial chromosome?

Prophage induction Signup and view all the answers

What is the key distinction of the lysogenic cycle compared to the lytic cycle?

It incorporates phage DNA into the bacterial genome Signup and view all the answers

What is a potential outcome for a bacterium that incorporates prophage DNA?

It may acquire new properties from the phage Signup and view all the answers

Which step occurs last in the lytic cycle?

Release of mature bacteriophages Signup and view all the answers

During specialized transduction, what happens to the bacterial DNA?

It is incorporated into a different bacterium Signup and view all the answers

What is the role of the tail fibers in bacteriophages?

To bind to the bacterial cell wall receptors Signup and view all the answers

Which of the following is NOT a component of the bacteriophage structure?

Ribosomes Signup and view all the answers

What is a mutation?

A permanent change in the DNA base sequence. Signup and view all the answers

Which of the following best describes a single-base mutation?

Replacement of one base in the DNA sequence with another base. Signup and view all the answers

What is a frame-shift mutation?

The addition or removal of one or more nucleotide pairs, changing the reading frame. Signup and view all the answers

What causes spontaneous mutations?

Mistakes during DNA replication. Signup and view all the answers

What is an induced mutation?

A mutation caused by exposure to mutagens such as chemicals or radiation. Signup and view all the answers

Which mechanism of gene transfer involves direct contact between two bacterial cells?

Conjugation Signup and view all the answers

Which statement is true about conjugation?

It requires the presence of a sex pilus and an F plasmid. Signup and view all the answers

What role does the F plasmid play in conjugation?

It carries the genes necessary for the formation of the sex pilus. Signup and view all the answers

Which of the following is NOT a method of gene transfer between bacterial cells?

Transcription Signup and view all the answers

What is the primary consequence of a mutation altering the DNA sequence?

It can potentially change the protein that is encoded. Signup and view all the answers

Which mechanism involves the transfer of DNA through a bacterial virus?

Transduction Signup and view all the answers

What is the primary method by which transformation occurs?

Uptake of DNA from the environment Signup and view all the answers

Which of the following is true about the competence of bacteria in transformation?

Only a few bacterial species can transform naturally. Signup and view all the answers

What occurs during the natural process of transformation?

Dying bacteria release their DNA for absorption. Signup and view all the answers

Which mechanism is characterized by its ability to be artificially induced?

Transformation Signup and view all the answers

Which of the following statements is false regarding transduction?

It can occur between any bacterial strains. Signup and view all the answers

What distinguishes transformation from transduction?

Transformation involves only DNA uptake, not a virus. Signup and view all the answers

Which of the following processes does not utilize a bacterial virus for DNA transfer?

Transformation Signup and view all the answers

What potential limitation does transformation have compared to transduction?

Transformation can only happen in dense bacterial populations. Signup and view all the answers

How is competence primarily defined in the context of bacterial transformation?

The innate capacity of bacteria to take up foreign DNA. Signup and view all the answers

Study Notes

Bacteriophage

Definition: Virus that infects bacteria.
Morphology of Bacteriophage
- Head: Hexagonal, contains nucleic acid core, with a protein coat (capsid).
- Tail: Hollow core surrounded by contractile sheath, ends by a plate with fibers.

Replication cycle

Bacteriophages can multiply by two alternative mechanisms: the lytic cycle or the lysogenic cycle.
The lytic cycle ends with the lysis and death of the host cell, whereas the host cell remains alive in the lysogenic cycle.

Lytic cycle

Attachment or adsorption: Bacteriophages use fibers at the end of the tail as attachment sites. The complementary receptor sites are on the bacterial cell wall.
Penetration: Bacteriophage injects its DNA (nucleic acid) into the bacterium.
Biosynthesis: Once the bacteriophage DNA has reached the cytoplasm of the host cell, the biosynthesis of viral nucleic acid and protein occurs.
Assembly: In this process, bacteriophage DNA and capsids are assembled into complete virion.
Release: The final stage of viral multiplication is the release of virions from the host cell after lysis.

Lysogenic cycle (Temperate cycle)

Some phages do not cause lysis and death of the host cell when they multiply. These lysogenic phages (also called temperate phages) capable of incorporating their DNA into the host cell's DNA to begin a lysogenic cycle.
The inserted phage DNA is now called a prophage.

Effect of prophage on the infected bacteria

Immunity to infection by another phage of the same type.
Acquire new properties

Outcome of the temperate cycle

Pass to daughter cells
Detach from the bacterial chromosome and start lytic cycle
Detach with a part of the bacterial chromosome and when infect another bacteria carries new properties of both the phage and the 1st bacterium (donor bacterium) and this called specialized transduction.

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Description

This quiz covers the definition, morphology, and replication cycles of bacteriophages, including detailed processes of the lytic and lysogenic cycles. Test your knowledge on how these viruses interact with bacteria and the mechanisms through which they multiply.