Virus Genome Replication Overview
48 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary difference in the number of proteins involved in bacterial versus eukaryotic DNA synthesis systems?

  • Eukaryotic systems involve fewer proteins.
  • Bacterial systems involve more proteins.
  • Both systems involve the same number of proteins.
  • Bacterial systems involve fewer proteins. (correct)

How is the Okazaki fragment synthesized during DNA replication?

  • Continuously on the leading strand.
  • Discontinuously on the lagging strand. (correct)
  • Using only one type of DNA polymerase.
  • In a single step with helicase.

Which mode of replication is also known as a rolling circle mode?

  • Semiconservative replication
  • Sigma mode (correct)
  • Theta mode
  • Conservative replication

In which type of replication do the daughter molecules each contain a strand of the original DNA?

<p>Semiconservative replication (B)</p> Signup and view all the answers

What are concatemers in the context of viral DNA replication?

<p>Very large DNA molecules composed of multiple copies of the virus genome. (B)</p> Signup and view all the answers

What are the two modes of replication for circular DNA genomes?

<p>Theta and sigma modes (C)</p> Signup and view all the answers

Which type of virus uses cell primase to synthesize RNA primers during its replication cycle?

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

What does the process of circularizing a linear DNA molecule mean?

<p>Joining the ends to form a closed loop. (C)</p> Signup and view all the answers

What role does the 3 –OH group in a polypurine tract play in retrovirus replication?

<p>It primes (+) DNA synthesis. (C)</p> Signup and view all the answers

Which polymerase is required by a DNA virus for genome replication?

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

Which type of replication may occur early and late in the infection cycle of some DNA viruses?

<p>Both theta and sigma modes (B)</p> Signup and view all the answers

Which class of viruses uses protein primers for nucleic acid replication?

<p>Some animal viruses and phages (A)</p> Signup and view all the answers

During latency, how is viral DNA treated during cell division?

<p>It gets incorporated and copied. (D)</p> Signup and view all the answers

What type of primer is used by hepadnaviruses to initiate (−) DNA synthesis?

<p>Protein primer (A)</p> Signup and view all the answers

What happens to the protein primers used by some viruses after their role is complete?

<p>They remain linked to the genome. (B)</p> Signup and view all the answers

Which polymerase do some viruses rely on from a host cell for genome replication?

<p>Both DNA and RNA polymerases (C)</p> Signup and view all the answers

What is the primary purpose of virus genome replication?

<p>To provide copies of the genome for progeny virions (D)</p> Signup and view all the answers

How do DNA viruses typically replicate their genomes?

<p>Directly to DNA (C)</p> Signup and view all the answers

What do plus-strand genomes have in common with the virus mRNA?

<p>They have the same sequence (C)</p> Signup and view all the answers

Which class of viruses replicates their (+) RNA genomes via a (−) RNA intermediate?

<p>Class IV (A)</p> Signup and view all the answers

What is the characteristic process of Class VII viruses?

<p>Reverse transcription from RNA to DNA (D)</p> Signup and view all the answers

What is the significance of single-stranded DNA in virus replication?

<p>It is converted to double-stranded DNA prior to copying (B)</p> Signup and view all the answers

What is the relationship between single-stranded genomes and their mRNA counterparts?

<p>One is complementary to the other (C)</p> Signup and view all the answers

Which of the following statements about RNA viruses is false?

<p>All RNA viruses replicate through reverse transcription (B)</p> Signup and view all the answers

What role does an endonuclease play during virion assembly?

<p>It cuts a genome length from a concatemer. (B)</p> Signup and view all the answers

Which mechanism do some dsRNA viruses use for genome replication?

<p>Both conservative and semi-conservative mechanisms. (C)</p> Signup and view all the answers

What is required for the synthesis of RNA molecules in ssRNA viruses?

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

Where are the genomes of most DNA viruses replicated?

<p>In the nucleus (A)</p> Signup and view all the answers

What is a notable characteristic of class IV viruses of eukaryotes?

<p>They replicate RNA in association with cytoplasmic membranes. (C)</p> Signup and view all the answers

In the replication process of dsRNA viruses, which enzyme is involved in unwinding the RNA?

<p>Helicase. (A)</p> Signup and view all the answers

Which of the following virus genomes is replicated solely in the cytoplasm?

<p>dsRNA (D)</p> Signup and view all the answers

What is unique about the replication of retroviruses?

<p>They convert RNA to DNA in the cytoplasm. (D)</p> Signup and view all the answers

What is the outcome in terms of strands during the semi-conservative replication of dsRNA?

<p>Each progeny molecule consists of one parental and one daughter strand. (B)</p> Signup and view all the answers

Which type of virus genome is replicated in the nucleus when segmented?

<p>(-) RNA (segmented genome) (B)</p> Signup and view all the answers

Where do many groups of viruses, including picornaviruses, derive their membranes from?

<p>The endoplasmic reticulum. (D)</p> Signup and view all the answers

Where must both plus- and minus-strand RNA have a binding site for RNA-dependent RNA polymerase?

<p>At the 3' end. (D)</p> Signup and view all the answers

All ssDNA virus genomes are replicated in which location?

<p>Nucleus (D)</p> Signup and view all the answers

Which of the following statements is correct regarding dsDNA viruses?

<p>Some dsDNA viruses replicate in the nucleus. (D)</p> Signup and view all the answers

In which of the following locations do most RNA viruses replicate?

<p>In the cytoplasm (B)</p> Signup and view all the answers

Which virus type has a unique replication process involving the conversion of RNA to DNA in the cytoplasm and DNA to RNA in the nucleus?

<p>Retroviruses (D)</p> Signup and view all the answers

What initiates the replication of many RNA viruses?

<p>The first nucleotide base pair with a nucleotide in the viral RNA (D)</p> Signup and view all the answers

Which reaction occurs first during the initiation of replication?

<p>Recognition of the initiation sequence by proteins (D)</p> Signup and view all the answers

What is required for the initiation of many DNA genomes replication?

<p>An RNA or protein primer (D)</p> Signup and view all the answers

How do ssDNA viruses such as parvoviruses initiate replication?

<p>By self-priming at the 3' end (B)</p> Signup and view all the answers

In the replication of cell DNA, what is synthesized after the double helix is unwound?

<p>Short sequences of RNA (B)</p> Signup and view all the answers

What is the role of the 3' –OH group during the initiation of DNA replication?

<p>It forms a linkage with the first nucleotide (A)</p> Signup and view all the answers

Which of the following statements about RNA primers is true?

<p>Only one RNA primer is needed for the entire leading strand (B)</p> Signup and view all the answers

How many primers are typically required for the Okazaki fragments during DNA replication?

<p>Several, as multiple primers are synthesized (C)</p> Signup and view all the answers

Flashcards

Virus Genome

The genetic material of a virus, which can be either DNA or RNA.

Virus Genome Replication

The process where the genome of a virus is replicated, creating new copies for progeny virions.

DNA vs RNA Virus Replication

DNA viruses generally replicate their genomes directly into DNA, while RNA viruses replicate their genomes directly into RNA.

Intermediate Replication

Some viruses replicate their genomes via an intermediate molecule, such as RNA for DNA viruses or DNA for RNA viruses.

Signup and view all the flashcards

Plus Strand (+) RNA Genome

A single-stranded RNA genome that has the same sequence as the virus's mRNA.

Signup and view all the flashcards

Minus Strand (-) RNA Genome

A single-stranded RNA genome that has the complementary sequence to the virus's mRNA.

Signup and view all the flashcards

Reverse Transcription

A process where a DNA molecule is synthesized from an RNA template.

Signup and view all the flashcards

Class VI Viruses

A class of viruses that replicate their genomes via a DNA intermediate, meaning they convert their RNA genome to a DNA copy before replicating.

Signup and view all the flashcards

Location of Virus Genome Replication

The location within a eukaryotic cell where a virus replicates its genome. This location can be either the cytoplasm or the nucleus.

Signup and view all the flashcards

dsDNA Viruses

Double-stranded DNA viruses. Some replicate in the cytoplasm while others replicate in the nucleus.

Signup and view all the flashcards

ssDNA Viruses

Single-stranded DNA viruses. All replicate in the nucleus.

Signup and view all the flashcards

dsRNA Viruses

Double-stranded RNA viruses. All replicate in the cytoplasm.

Signup and view all the flashcards

(+) RNA Viruses

Positive-sense RNA viruses. All replicate in the cytoplasm.

Signup and view all the flashcards

(-) RNA Viruses (non-segmented)

Negative-sense RNA viruses with a single RNA molecule. All replicate in the cytoplasm.

Signup and view all the flashcards

(-) RNA Viruses (segmented)

Negative-sense RNA viruses with multiple RNA segments. All replicate in the nucleus.

Signup and view all the flashcards

Replication Initiation Site

The specific sequence on a virus genome where nucleic acid replication begins.

Signup and view all the flashcards

Primer

A molecule, usually RNA or protein, that initiates nucleic acid replication by providing a free 3'-OH group for the first nucleotide to attach to.

Signup and view all the flashcards

Self-priming

A special type of primer used in certain viruses where a complementary sequence at the 3' end of the DNA folds back on itself, creating a free 3'-OH group for initiation.

Signup and view all the flashcards

DNA Unwinding

The process of unwinding the double helix of DNA using an enzyme called helicase, allowing for the synthesis of new strands.

Signup and view all the flashcards

Primase

An enzyme that synthesizes short RNA sequences complementary to the DNA template, serving as primers for DNA replication.

Signup and view all the flashcards

Leading Strand

The continuous strand of DNA synthesized during replication, using only one primer.

Signup and view all the flashcards

Lagging Strand

The discontinuous strand of DNA synthesized during replication, requiring multiple primers for each short fragment (Okazaki fragments).

Signup and view all the flashcards

Okazaki Fragments

Short fragments of DNA synthesized on the lagging strand during replication, each requiring its own primer.

Signup and view all the flashcards

What is the primer used by retroviruses for (−) DNA synthesis?

Some viruses, like retroviruses, use their host's existing transfer RNA (tRNA) to prime the synthesis of their DNA from a (+) RNA template. This tRNA acts as a starting point for DNA synthesis, allowing the virus to replicate its genome.

Signup and view all the flashcards

How does a retrovirus prime (+) DNA synthesis?

In retroviruses, the 3'-OH group of a polypurine tract within the partially degraded (+) RNA template is used as a primer for (+) DNA synthesis. This allows the virus to synthesize a complementary strand of DNA, completing the process of DNA replication.

Signup and view all the flashcards

Do all viruses use nucleic acid primers?

Some DNA viruses, such as adenoviruses, utilize a protein as a primer to initiate DNA replication. These protein primers are typically found linked to the 5' ends of the viral genome in virions.

Signup and view all the flashcards

What is the difference in the replication process of viruses that utilize protein primers?

The process of viral genome replication is essential for the virus to produce new progeny viruses. Some viruses have evolved to use both RNA primers and protein primers for different stages of their replication cycle.

Signup and view all the flashcards

What are the key enzymes in virus genome replication?

DNA polymerases and RNA polymerases are the key enzymes involved in replicating viral genomes, essentially copying the viral genetic information. These enzymes can either be encoded by the virus itself or borrowed from the host cell.

Signup and view all the flashcards

What specific type of polymerase do DNA viruses that reside in eukaryotic nuclei need?

DNA viruses that replicate in the nuclei of eukaryotic cells require a DNA-dependent DNA polymerase. These viruses need this enzyme specifically to copy DNA from a DNA template.

Signup and view all the flashcards

How does a hepadnavirus initiate both (−) and (+) DNA synthesis?

Hepadnaviruses are unique in that they utilize both a protein primer to initiate the synthesis of their (−) DNA strand and an RNA primer to initiate the synthesis of their (+) DNA strand.

Signup and view all the flashcards

What happens to the protein and RNA primers after use?

Protein primers, as well as the RNA primers used by hepadnaviruses, are not removed after they have served their purpose in initiating DNA synthesis. They remain linked to the 5' ends of the viral genome in virions.

Signup and view all the flashcards

Leading & Lagging Strands

In DNA replication, one daughter strand is synthesized continuously, called the leading strand, while the other is synthesized discontinuously, called the lagging strand. This lagging strand is synthesized in short fragments, called Okazaki fragments, which are later joined by DNA ligase.

Signup and view all the flashcards

Semiconservative Replication

DNA replication is the process of duplicating a DNA molecule to create two identical copies. It is called semiconservative because each new DNA molecule contains one original strand and one newly synthesized strand.

Signup and view all the flashcards

Linear DNA Circularization

Linear DNA molecules can be circularized before replication. After replication, they can be separated into individual circular molecules.

Signup and view all the flashcards

Theta & Sigma Replication

The theta mode of replication is a form of DNA replication where the DNA molecule opens up like a theta symbol (θ) and replicates bidirectionally. In the sigma mode (rolling circle), one strand acts as a template for continuous replication, while the other is displaced as a single-stranded copy.

Signup and view all the flashcards

Concatemers

Concatemers are very long DNA molecules composed of multiple copies of the viral genome. They are formed during the replication of some viruses like herpesviruses and T4 phage.

Signup and view all the flashcards

Viral Replication Modes

In some viruses, the theta replication mode is used early in infection, while the sigma mode is used late in infection. This switch in replication modes might be linked to different stages of the viral lifecycle.

Signup and view all the flashcards

Helicase-Primase Complex

The helicase-primase complex is a group of enzymes that function together in DNA replication. Helicase unwinds the DNA double helix, and primase synthesizes short RNA primers to start DNA synthesis.

Signup and view all the flashcards

Replication in Prokaryotes vs Eukaryotes

The process and enzymes involved in DNA replication vary between prokaryotes and eukaryotes. Bacterial systems typically require fewer proteins for replication compared to eukaryotic systems.

Signup and view all the flashcards

Conservative Replication

A mechanism where the original viral genome (parental) remains intact, and a completely new genome (daughter) is created.

Signup and view all the flashcards

RNA Helicase

An enzyme that unwinds the double-stranded RNA molecule, separating the two strands to allow replication.

Signup and view all the flashcards

RNA-dependent RNA Polymerase

An enzyme that uses an RNA template to synthesize a new RNA molecule. This is crucial for the replication of RNA viruses.

Signup and view all the flashcards

Cytoplasmic Replication of RNA Viruses

A class of viruses that replicate their RNA genomes in association with cytoplasmic membranes, often derived from the endoplasmic reticulum.

Signup and view all the flashcards

Study Notes

Virus Genome Replication

  • Virus genome replication is the fifth step in the generalized replication cycle
  • The infecting virus's genome is replicated to amplify viral transcription and produce progeny virions' genomes
  • DNA viruses replicate their genomes directly into DNA, while RNA viruses replicate their genomes directly into RNA
  • Some DNA viruses replicate via RNA intermediates, and some RNA viruses replicate via DNA intermediates
  • Replication modes of virus genomes are summarized in Figure 7.1

Single-Stranded Genomes

  • Single-stranded genomes are designated as + or -, based on their relationship to the virus's mRNA
    • strand genomes have the same sequence as the mRNA (except in DNA where thymine replaces uracil)
    • strand genomes have a sequence complementary to the mRNA (except in DNA where thymine replaces uracil)
  • Single-stranded DNA is converted into double-stranded DNA before copying

Replication in Eukaryotic Cells

  • Virus genomes are delivered to the cytoplasm or nucleus
  • The location of replication varies based on the genome type (see Table 7.1)
  • Most DNA viruses replicate in the nucleus
  • Some double-stranded DNA viruses replicate in the cytoplasm
  • Most RNA viruses replicate in the cytoplasm
  • Minus-strand RNA viruses with segmented genomes replicate in the nucleus
  • Retroviruses and pararetroviruses produce DNA from RNA in the cytoplasm and RNA from DNA in the nucleus

Initiation of Genome Replication

  • Each virus genome has a specific sequence where replication starts, recognized by initiation proteins
  • Replication requires priming, the first reaction of a nucleotide with an -OH group at the initiation site
  • RNA viruses (e.g., rotaviruses, rhabdoviruses) initiate with the first nucleotide base-pairing with a nucleotide in the viral RNA
  • This initial nucleotide acts as a primer for RNA replication
  • Some single-stranded DNA viruses (like parvoviruses) use self-priming, using complementary regions at the 3' end of the DNA

RNA and Protein Primers

  • DNA synthesis starts after a helicase unwinds a region of the double helix
  • A primase synthesizes short RNA sequences that are complementary to DNA regions
  • These RNAs (primers) are required for initiating the leading strand synthesis
  • Multiple primers are required for Okazaki fragments in the lagging strand
  • The 3'-OH group of the primer RNA is linked to the first nucleotide of the new DNA sequence

Polymerases

  • Viruses use DNA or RNA polymerases for genome replication
  • Some viruses encode their own polymerases, while others utilize host cell enzymes
  • DNA viruses requiring DNA-dependent DNA polymerisation
  • Viruses with small genomes often use a cell's enzyme, while viruses with large genomes typically encode their own
  • RNA viruses require RNA-dependent RNA polymerase as the replicase enzyme
  • Retroviruses utilize a reverse transcriptase to convert RNA into DNA

DNA Replication

  • DNA viruses in Class I and II replicate their genome via dsDNA
  • Single-stranded DNA viruses first synthesize a complementary strand to form dsDNA
  • Replication initiates at specific DNA sequences called origins of replication
  • Proteins involved in DNA replication include helicases, single-stranded DNA binding proteins, and DNA polymerases

Double-Stranded RNA Replication

  • Double-stranded RNA (dsRNA) genomes need to be unwound by a helicase prior to replication
  • Some dsRNA viruses replicate via a semi-conservative mechanism, similar to dsDNA
  • Other dsRNA viruses use a conservative mechanism of replication
  • (Figure 7.6) illustrates the conservative mechanism

Single-Stranded RNA Replication

  • Single-stranded RNA (ssRNA) replication in Classes IV and V involves the synthesis of complementary RNA strands, using the original strand as a template
  • RNA-dependent RNA polymerase is recruited to the 3' end of the template
  • Both + and - strand RNAs have a binding site for the polymerase at their 3' ends

Reverse Transcription

  • Some RNA viruses use a DNA intermediate in their replication, while some DNA viruses utilize an RNA intermediate
  • Reverse transcription involves two major steps: converting (+) RNA into (-) DNA, and synthesizing a second DNA strand
  • This process is catalyzed by a reverse transcriptase, an enzyme encoded by the virus
  • Reverse transcription takes place inside the infected cell's viral structure

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Virus Genome Replication PDF

Description

Explore the intricate process of virus genome replication, the essential fifth step in the viral replication cycle. This quiz covers the distinctions between DNA and RNA viruses, single-stranded genome classifications, and replication mechanics in eukaryotic cells. Test your understanding of viral genome amplification and transcription methods.

More Like This

Understanding Virus Genome and Discovery
0 questions

Understanding Virus Genome and Discovery

CelebratoryAmazonite avatar
CelebratoryAmazonite
Viral Replication Steps Quiz
30 questions

Viral Replication Steps Quiz

LucidCypress avatar
LucidCypress
Viral Genome Entry and Replication Mechanisms
18 questions

Viral Genome Entry and Replication Mechanisms

FastGrowingPeachTree avatar
FastGrowingPeachTree
Virology: Virus Classification and Genome Replication
10 questions

Virology: Virus Classification and Genome Replication

StunnedBougainvillea avatar
StunnedBougainvillea
Use Quizgecko on...
Browser
Open
Browser
Browser