Viral Replication Process Quiz

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Questions and Answers

Which enzyme is required for the replication of plus sense ssRNA viruses?

  • RNA dependent RNA polymerase (correct)
  • RNA replicase
  • Reverse transcriptase
  • DNA polymerase

What is a primary characteristic of the lysogenic replication cycle?

  • Utilizes circular genomes exclusively
  • Always results in viral progeny
  • Involves integration into the host genome (correct)
  • Directly destroys the host cell

How does the lytic cycle of viral replication primarily differ from the lysogenic cycle?

  • Lytic cycle retains viral DNA within host
  • Lytic cycle leads to rapid cell lysis (correct)
  • Lytic cycle results in slow integration into host DNA
  • Lytic cycle involves phage repressor proteins

What is the 'end problem' in linear genomes during viral replication?

<p>Inability to fully replicate the genetic material (C)</p> Signup and view all the answers

What is a concatemers' role in viral replication?

<p>Forming a linear structure of multiple genomes (B)</p> Signup and view all the answers

What type of viruses are capable of undergoing lysogeny?

<p>Temperate phages (B)</p> Signup and view all the answers

Which scenario triggers the lytic cycle in a temperate phage?

<p>Inactivation of a phage repressor protein (D)</p> Signup and view all the answers

What is a prophage in the context of viral replication?

<p>Viral DNA integrated into the host genome (B)</p> Signup and view all the answers

What type of genome does HIV contain?

<p>linear ssRNA (+) (C)</p> Signup and view all the answers

What is the primary function of reverse transcriptase in the retrovirus replication cycle?

<p>To convert ssRNA into dsDNA (B)</p> Signup and view all the answers

Retroviruses primarily replicate through which of the following types of viral enzymes?

<p>RNA-dependent DNA polymerase (D)</p> Signup and view all the answers

What mechanism allows retroviruses to solve the end problem during replication?

<p>Employing terminal repeats in their genome (D)</p> Signup and view all the answers

What primarily contributes to the high mutation rate of RNA viruses?

<p>Their viral polymerases have high error rates (D)</p> Signup and view all the answers

Why are DNA viruses less common in animals compared to bacteria?

<p>Eukaryotic cells compartmentalize DNA replication (B)</p> Signup and view all the answers

What function does the integrase provide during the retroviral replication cycle?

<p>Integrate dsDNA into the host genome (D)</p> Signup and view all the answers

Which activity does not belong to the reverse transcriptase enzyme?

<p>RNA-dependent RNA polymerase activity (C)</p> Signup and view all the answers

What role does the lambda repressor (cI) play in the lysogenic replication cycle?

<p>It represses the expression of the cro promoter. (C)</p> Signup and view all the answers

Which element is responsible for triggering the lytic pathway?

<p>Cro repressor (C)</p> Signup and view all the answers

What is the initial condition that favors the stability of the CII protein during infection?

<p>Favorable environmental conditions (A)</p> Signup and view all the answers

What is the primary function of the lambda integrase during lysogeny?

<p>To facilitate the integration of the phage genome into the bacterial genome (D)</p> Signup and view all the answers

What outcome results from a non-sense mutation in the cro repressor?

<p>Stability of the lysogenic state will increase. (C)</p> Signup and view all the answers

Which of the following best describes rolling circle replication?

<p>It utilizes a circular single-stranded DNA template. (B)</p> Signup and view all the answers

In the context of lambda phage, what does the activity of RecA imply?

<p>It cleaves the lambda repressor, facilitating lytic cycle induction. (C)</p> Signup and view all the answers

Which combination of mutations would potentially trap a lambda prophage within a bacterial genome?

<p>A non-sense mutation in the cro repressor and a silent mutation in the integrase gene (D)</p> Signup and view all the answers

Flashcards

Temperate phage

A type of virus that can replicate using the lytic cycle or the lysogenic cycle. It can integrate its DNA into the host genome, becoming a prophage.

Lysogeny

The state in which a temperate phage integrates its DNA into the host genome, leading to the replication of viral DNA along with the host DNA.

Prophage

The viral DNA that is integrated into the host genome during lysogeny.

Lytic replication cycle

A viral replication cycle that results in the lysis (burst) of the host cell, releasing newly formed viral particles.

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Circular permutation

A common way to solve the 'end problem' of replicating linear genomes in T4 phage. It involves linking multiple copies of the genome together, end-to-end.

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RNA replicase (RNA-dependent RNA polymerase)

A special type of RNA polymerase found in viruses that can create a new RNA strand using an RNA template.

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Reverse transcriptase

A special type of enzyme found in retroviruses that can synthesize DNA from RNA.

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Viral replication

The process of a virus replicating its genome and producing new viral particles within a host cell.

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Lambda Phage Circularization

The cohesive ends of the lambda phage DNA genome allow for circularization, which is necessary for both the lytic and lysogenic pathways.

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Rolling Circle Replication

A type of DNA replication used by the lambda phage in the lytic cycle, where the genome is synthesized and cut at the cos site.

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Theta Replication

A type of DNA replication used by bacteria and other organisms, where two replication forks start at a specific origin of replication (ori) and move in opposite directions.

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Lambda Integrase

A phage-encoded enzyme that integrates the lambda phage DNA into the bacterial chromosome, initiating lysogeny.

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Lambda Repressor (cI)

A regulatory protein in lambda phage that controls the switch between the lytic and lysogenic pathways.

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Cro Repressor (cro)

A regulatory protein in lambda phage that activates the lytic pathway.

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Lambda Activator II (CII)

A regulatory protein in lambda phage that triggers lysogeny upon infection.

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Retrovirus

A type of virus that contains a single-stranded RNA (+) genome and uses a double-stranded DNA intermediate to integrate into the host genome.

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Integrase

An enzyme found in retroviruses that integrates the double-stranded DNA copy of the viral genome into the host's genome.

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Linear ssRNA (+) genome in retroviruses

A unique feature of retroviruses, where the viral genome is linear single-stranded RNA (+).

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The 'end problem' of linear genomes

A problem faced by viruses with linear genomes. The ends of the genome can be lost during replication, affecting the integrity of the viral genome.

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Terminal repeats in retroviruses

A mechanism used by retroviruses to solve the 'end problem' with their linear genomes.

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High error rate in viral replication

The process by which a virus uses its own polymerase to replicate its genome with a high rate of error

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Proviral state

The process of a virus integrating its genetic material into the host's genome, leading to long-term persistence.

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Study Notes

Viral Replication

  • Viral replication involves various processes depending on the viral type (DNA or RNA).
  • Different classes of viruses have distinct replication strategies.
  • DNA viruses (Class I & VII) typically replicate through semi-conservative replication.
  • RNA viruses (Classes II-VI) employ diverse replication mechanisms.
  • Retroviruses (Class VI) use reverse transcriptase to convert RNA into DNA.
  • Some viruses integrate their genetic material into the host's genome (e.g., retroviruses and temperate phages).

Problems in Viral Replication

  • Linear genomes pose challenges during replication.
  • Circular permutation for T4 phage solves the end problem of replicating linear genomes.
  • Terminal redundancy in certain phages (e.g., T4) aids in replication.
  • Formation of concatemers by joining ends creates long DNA molecules for multiple viral genomes.
  • Certain viruses (e.g., HIV) employ terminal repeats to copy their ends during replication.
  • Some viruses use terminal proteins or other molecules as primers for replication.
  • Host DNA replication processes are impacted during viral replication.

Temparate Phage and Lysogeny

  • Temperate phages can undergo both lytic and lysogenic cycles.
  • Lysogeny involves viral DNA integrating into the host genome.
  • Lysogenic viral DNA (prophage) replicates along with the host DNA, producing multiple prophage copies.
  • The lysogenic pathway is often induced during adverse conditions, triggering the lytic cycle.

Retrovirus Replication

  • Retroviruses use reverse transcriptase to convert their RNA genome into DNA.
  • The integrated DNA is then transcribed and translated to form new viral components.
  • Retroviruses employ terminal repeats to address the end-problem.

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