Microbiology: Virology Lecture 3 - Viral Replication Cycle

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Questions and Answers

Which of the following is true about viruses?

Viruses are obligate intracellular parasites. (correct)

Viruses can produce their own energy sources for replication.

Viruses are able to replicate independently without a host cell.

Viruses only require their own genetic material for replication.

What is the role of the host cell in viral replication?

Host cells produce the required receptors for viral entry, but cannot support viral replication.

Host cells are resistant to viral infection and do not allow any viral replication to occur.

Host cells provide the necessary machinery, energy sources, and enzymes for viral genome replication and translation of viral mRNAs. (correct)

Host cells are only permissive to viral replication, and do not provide any other functions for the virus.

What is the difference between a susceptible cell and a permissive cell?

A susceptible cell is resistant to viral infection, while a permissive cell is able to be infected by the virus.

A susceptible cell may or may not be able to support viral replication, while a permissive cell can support viral replication. (correct)

A susceptible cell produces the required receptors for viral entry, while a permissive cell does not.

A susceptible cell can support viral replication, while a permissive cell cannot.

What is the first step in the viral replication cycle?

Attachment and entry Signup and view all the answers

Which of the following is a characteristic of RNA viruses?

They rely on the host cell's machinery for translation of viral mRNAs. Signup and view all the answers

What is the role of reverse transcriptase in the viral replication cycle?

It converts the viral RNA genome into a DNA provirus that integrates into the host cell's genome. Signup and view all the answers

What is the difference between the replication cycles of DNA viruses and RNA viruses?

DNA viruses rely on host cell DNA-dependent DNA polymerase for genome replication, while RNA viruses rely on host cell RNA-dependent RNA polymerase. Signup and view all the answers

Which of the following is a characteristic of DNA viruses?

They can directly integrate their genome into the host cell's chromosome. Signup and view all the answers

What is the role of viral mRNA synthesis in the viral replication cycle?

It facilitates the translation of viral proteins required for genome replication and assembly. Signup and view all the answers

Which of the following is a characteristic of the viral replication cycle?

Viruses rely on the host cell's machinery and resources for various steps of the replication cycle. Signup and view all the answers

What is the primary function of reverse transcriptase in viral replication?

Synthesizing DNA from RNA Signup and view all the answers

In viral replication, which type of viruses package the viral RNA-dependent RNA polymerase along with the genome?

dsRNA viruses Signup and view all the answers

Which enzyme is responsible for synthesizing long chains of nucleic acids in most DNA viruses?

DNA-dependent DNA polymerase Signup and view all the answers

What is the general mechanism of entry into host cells for non-enveloped viruses?

Disrupting the lysosomal membrane Signup and view all the answers

Which step of the viral replication cycle involves acquisition of an envelope in some viruses?

Release Signup and view all the answers

How do enveloped viruses primarily exit host cells during release?

B and C Signup and view all the answers

Which classification of viral genomes includes RNA genomes that use reverse transcriptase during replication?

Type III Signup and view all the answers

Study Notes

Viruses Overview

Viruses are acellular infectious agents that require a host cell for replication.
They can be classified based on their genetic material into RNA and DNA viruses, each with distinct characteristics and replication mechanisms.

Role of the Host Cell

The host cell provides the necessary machinery and environment for viral replication.
Viruses hijack the host's cellular processes to produce new virus particles.

Susceptible vs. Permissive Cells

Susceptible cells are those that have the receptors necessary for virus attachment and entry.
Permissive cells allow for viral replication and assembly, providing the environment for the virus to proliferate.

First Step in the Viral Replication Cycle

Attachment of the virus to the host cell surface, followed by penetration of the viral genome into the host cell.

Characteristics of RNA Viruses

RNA viruses generally have higher mutation rates due to the lack of proofreading mechanisms during replication.

Role of Reverse Transcriptase

Reverse transcriptase converts viral RNA into DNA, allowing the virus to integrate into the host's genome or utilize the DNA for replication.

Replication Cycles of DNA vs. RNA Viruses

DNA viruses typically replicate in the host cell nucleus using host enzymes, while RNA viruses usually replicate in the cytoplasm using their own viral enzymes.

Characteristics of DNA Viruses

DNA viruses often have more stable genomes and typically rely on host DNA polymerases for replication.

Viral mRNA Synthesis

Synthesis of viral mRNA is crucial for the production of viral proteins, allowing the virus to hijack the host's protein synthesis machinery.

Characteristics of the Viral Replication Cycle

The cycle includes attachment, penetration, uncoating, replication, assembly, and release.

Primary Function of Reverse Transcriptase

It reverses the transcription process, creating DNA from RNA, which is vital for certain types of viruses, mainly retroviruses.

Packaging of RNA-Dependent RNA Polymerase

RNA viruses, particularly those that replicate through an RNA intermediate, package RNA-dependent RNA polymerase with their genomes to enable replication upon entering host cells.

Enzyme for DNA Virus Nucleic Acid Synthesis

DNA polymerase catalyzes the synthesis of long chains of nucleic acids in most DNA viruses.

Entry Mechanism for Non-Enveloped Viruses

Non-enveloped viruses typically enter host cells through direct membrane penetration or endocytosis without needing an envelope.

Acquisition of Envelope

Some viruses acquire their envelope during the budding process, which occurs as new viral particles exit the host cell.

Exit Mechanism for Enveloped Viruses

Enveloped viruses mainly exit host cells via budding, allowing them to take a portion of the host cell membrane.

Classification of Viral Genomes

Retroviruses possess RNA genomes and utilize reverse transcriptase during their replication cycle, integrating into the host genome.

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Description

Learn about the viral replication cycle in this introduction to microbiology lecture. Understand how viruses are obligate intracellular parasites and require host cell functions for reproduction of new infectious particles.