Biology Chapter: Viruses Overview

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Questions and Answers

What type of polymerase is required by RNA viruses?

RNA-dependent DNA polymerase

RNA-dependent RNA polymerase (correct)

DNA-dependent RNA polymerase

DNA-dependent DNA polymerase

Which of the following RNA viruses is associated with haemorrhagic fever?

Hepatitis C

Rubella

Common cold

Yellow fever (correct)

What type of nucleic acid do enteroviruses contain?

Single-stranded (-) RNA

Double-stranded RNA

Single-stranded (+) RNA (correct)

Double-stranded DNA

Which of the following viruses is classified as the largest RNA virus?

Coronavirus Signup and view all the answers

Which family includes viruses that cause respiratory infections?

Coronaviruses Signup and view all the answers

What type of genetic material can a virus have?

Both DNA and RNA Signup and view all the answers

What is the benefit of a virus having an envelope made from host membrane phospholipids?

It helps disguise the virus from the host's immune system. Signup and view all the answers

Which component is primarily responsible for protecting the virus's genetic material?

Envelope Signup and view all the answers

What describes the overall structure of the complete infectious virus particle?

Virion Signup and view all the answers

How do new virions form within a host cell?

By assembly of building blocks directed by viral genetic material Signup and view all the answers

What characteristic distinguishes nonenveloped viruses from enveloped viruses?

Nonenveloped viruses are generally more stable than enveloped viruses. Signup and view all the answers

What role do capsomeres play in a virus?

They are structural proteins that compose the capsid. Signup and view all the answers

What does virion symmetry refer to in virology?

The arrangement of capsomere units in the viral capsid. Signup and view all the answers

What is the primary method of replication for Hepadnaviruses?

Reverse transcription inside the virus particle Signup and view all the answers

Which statement accurately describes the replication location for DNA viruses?

Most replicate in the nucleus, except poxvirus Signup and view all the answers

What feature distinguishes RNA viruses from DNA viruses?

Only +RNA virus genomes are infectious Signup and view all the answers

Which viral characteristic is associated with all (-) RNA viruses?

All carry RNA polymerase Signup and view all the answers

Which statement accurately describes the infectiousness of DNA viruses compared to RNA viruses?

Genomic material of DNA viruses is infectious, RNA viruses typically are not Signup and view all the answers

How do segmented RNA viruses change their genetic material?

Through reassortment of genome segments Signup and view all the answers

What is a common feature of DNA viruses compared to RNA viruses?

DNA viruses generally require host RNA polymerase Signup and view all the answers

What is NOT a criterion for the classification of viruses?

Host preference Signup and view all the answers

What is the defining characteristic of Group 4 viruses in the Baltimore classification?

They act as mRNA for protein synthesis Signup and view all the answers

How is negative-sense RNA synthesized for protein production?

It is transcribed to form complementary-sense strands Signup and view all the answers

Which Baltimore classification group does not act as mRNA?

Group 5: SS RNA (-) Signup and view all the answers

Which statement about transcription in Group 4 viruses is correct?

It requires the RNA to be converted from 3' to 5' Signup and view all the answers

Which of the following is NOT true in the context of SS Retro RNA?

It can be synthesized without reverse transcription Signup and view all the answers

What type of genome does Group 3 in the Baltimore classification have?

Double-stranded RNA Signup and view all the answers

What is the impact of a virus categorized under Group 1?

It is double-stranded DNA that acts as a template for mRNA synthesis Signup and view all the answers

What does the Baltimore classification system primarily classify?

Viruses based on their replication methods and genome types Signup and view all the answers

Which process is necessary for negative-sense RNA viruses to produce mRNA?

Transcription Signup and view all the answers

What is one of the characteristics of single-stranded RNA viruses?

They can be either positive-sense or negative-sense. Signup and view all the answers

Which of the following viruses is classified as a Bunyavirus?

Hanta virus Signup and view all the answers

What is the primary replication strategy of Retroviruses?

Integration of genetic material into the host cell's DNA Signup and view all the answers

Which virus is associated with gastroenteritis?

Rota virus Signup and view all the answers

How does the influenza virus enter a host cell?

Via receptor-mediated endocytosis Signup and view all the answers

What type of genetic material does Calicivirus possess?

Single-stranded positive sense RNA Signup and view all the answers

Which of the following statements is true regarding Rhabdoviruses?

Rabies virus is a member of this group. Signup and view all the answers

Which characteristic distinguishes Paramyxoviruses?

They are associated with respiratory infections. Signup and view all the answers

What is a key feature of Ebola virus?

It is known for causing hemorrhagic fever. Signup and view all the answers

What distinguishes the genetic material of Reoviruses?

It is double-stranded and segmented. Signup and view all the answers

What type of RNA is associated with Hanta viruses?

Single-stranded RNA with negative sense Signup and view all the answers

Which of the following correctly describes the Baltimore classification of viruses?

It is based on genetic contents and replication strategies. Signup and view all the answers

What is unique about the replication of the influenza virus?

It has a segmented RNA genome that replicates in the nucleus. Signup and view all the answers

What type of disease is primarily linked to Arenaviruses?

Meningitis Signup and view all the answers

Which of the following viruses is classified under the family of Caliciviruses?

Norwalk virus Signup and view all the answers

Study Notes

Virus Characteristics

Viruses are obligate intracellular parasites, requiring host cells for reproduction.
Contain either DNA or RNA as genetic material, never both.
Viral genetic material directs the synthesis of new virions within host cells.
New virions assemble from building blocks in host cells and spread to infect other cells.

Basic Virus Components

Virion: Complete infectious virus particle.
Capsid: Protein coat that protects nucleic acids and has antigenic properties.
Capsomeres: Protein subunits forming the capsid; more stable than lipids, making non-enveloped viruses generally more stable.
Envelope: Phospholipid membrane derived from the host cell, facilitating entry into host cells and featuring proteins that enable specific adhesion via receptor binding domains.

Virus Replication Process

Virus binds to host cell using receptor spikes.
Entry occurs through fusion with the host membrane or endocytosis.
The virus utilizes host cell machinery for replication and protein synthesis.
Influenza virus replication occurs in the nucleus due to its segmented genome.
HIV integrates its genetic material into the host genome, distinguishing it from other viruses.

Baltimore Classification

Developed by David Baltimore, classifies viruses by nucleic acid type and replication strategies.
Types include:
- DS DNA: Double-stranded DNA viruses.
- SS DNA: Single-stranded DNA viruses.
- DS RNA: Double-stranded RNA viruses.
- SS RNA (+): Positive-sense single-stranded RNA viruses, can act directly as mRNA.
- SS RNA (-): Negative-sense RNA viruses, must be transcribed to produce mRNA.
- SS Retro RNA (+): Retroviruses, which synthesize DNA from RNA through reverse transcription.

Virus Dynamics

DNA viruses: Generally permanent, replicate in the nucleus, and their genomic material is infectious.
RNA viruses: Short-lived, primarily replicate in the cytoplasm (exceptions exist for certain groups).
All negative-sense RNA viruses have envelopes and contain RNA polymerase for replication.
Segmented RNA viruses possess the ability to alter their composition through reassortment.

Classification Summary

Classification of viruses considers nucleic acid type, strand number, genome polarity, capsid symmetry, presence of envelope, and other genetic and antigenic properties.

Viral Release Mechanisms

Viruses exit host cells through either lysis (cell destruction) or budding (acquisition of an envelope).

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Description

Explore the fundamental properties and behavior of viruses as distinct biological entities. This quiz covers their characteristics, genetic material, and reproduction within a host cell. Test your understanding of these infectious agents and their unique lifecycle.