Genome and Capsid Structure of Viruses

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Questions and Answers

What type of genetic material do DNA viruses contain?

dsDNA (correct)

ssDNA (correct)

ssRNA

dsRNA

What is the typical genome size range for RNA viruses?

3,000 to 30,000 bases

What is an example of a DNA virus?

Herpes simplex virus (HSV)

DNA is more chemically unstable than RNA.

False Signup and view all the answers

How are RNA viruses primarily characterized in terms of their genome?

Single-stranded positive-sense or negative-sense Signup and view all the answers

What type of symmetry do DNA virus capsids typically have?

Icosahedral symmetry Signup and view all the answers

What role does the viral envelope play for RNA viruses?

It protects the RNA genome Signup and view all the answers

Which RNA virus is an example of an enveloped virus?

Influenza virus Signup and view all the answers

The Herpesviruses are examples of __________ viruses.

enveloped DNA Signup and view all the answers

What type of genetic material do DNA viruses contain?

Either double-stranded (dsDNA) or single-stranded (ssDNA) DNA Signup and view all the answers

Which statement is true regarding RNA viruses?

Their genome size is smaller than that of DNA viruses. Signup and view all the answers

DNA viruses generally have larger genomes than RNA viruses.

True Signup and view all the answers

What is the shape of the capsid of DNA viruses usually?

Icosahedral symmetry Signup and view all the answers

Which virus example contains linear double-stranded DNA?

Herpes simplex virus Signup and view all the answers

What primary function does the viral envelope serve in RNA viruses?

Protecting the fragile RNA genome and assisting in attachment to host cells Signup and view all the answers

RNA viruses are generally more stable than DNA viruses.

False Signup and view all the answers

Match the following virus examples with their characteristics:

Herpes simplex virus = Linear dsDNA SARS-CoV-2 = Single-stranded positive-sense RNA Rabies virus = Helical symmetry capsid Influenza virus = Enveloped RNA virus Signup and view all the answers

Study Notes

Genome Architecture

DNA viruses contain either double-stranded (dsDNA) or single-stranded (ssDNA) DNA
RNA viruses carry single-stranded (ssRNA) or double-stranded (dsRNA) RNA
DNA viruses generally have larger genomes compared to RNA viruses
RNA viruses have smaller genomes, limiting the number of proteins they encode
DNA is more stable than RNA, making DNA viruses structurally more stable
RNA is more chemically unstable, contributing to a high mutation rate in RNA viruses
The herpes simplex virus (HSV) contains linear dsDNA
SARS-CoV-2 has a single-stranded positive-sense RNA genome

Capsid Structure

The capsid is the protein shell that encases the viral genome
DNA viruses generally have well-organized and symmetrical capsids, often with icosahedral symmetry
RNA viruses have simpler and less symmetrical capsids due to the smaller genome and RNA instability
Many RNA viruses have helical symmetry
DNA virus capsids are made of repetitive protein subunits that self-assemble
RNA viruses also use repetitive protein subunits to build their capsids
The Adenovirus has an icosahedral capsid structure
Rabies virus has a bullet-shaped capsid with helical symmetry

Viral Envelope

Some DNA viruses and RNA viruses are enveloped, meaning they have an outer lipid membrane derived from the host cell membrane
Enveloped viruses use the envelope to fuse with the host cell membrane for entry
Envelope proteins are essential for recognizing and attaching to host cell receptors
Herpesviruses are enveloped DNA viruses, utilizing glycoproteins for host cell entry
The envelope helps RNA viruses attach to host cells and avoid the immune system
The Influenza virus is an enveloped RNA virus, with hemagglutinin (HA) and neuraminidase (NA) glycoproteins on its surface

Genome Architecture

DNA viruses contain either double-stranded (dsDNA) or single-stranded (ssDNA) DNA as their genetic material.
DNA viruses generally have larger genomes compared to RNA viruses, sometimes comprising several hundred thousand base pairs.
DNA viruses can be circular or linear, depending on the virus.
DNA is more stable than RNA, making DNA viruses structurally more stable and less prone to genetic damage or degradation.
RNA viruses carry single-stranded (ssRNA) or double-stranded (dsRNA) RNA as their genetic material.
Some single-stranded RNA is either positive-sense (+) or negative-sense (-).
RNA viruses have smaller genomes, typically ranging from 3,000 to 30,000 bases, which limits the number of proteins they encode.
RNA is single-stranded or double-stranded, with RNA viruses often having a segmented genome (e.g., influenza virus) that allows for genetic variability.
RNA is more chemically unstable and susceptible to degradation compared to DNA, contributing to the virus's high mutation rate.

Capsid Structure

The capsid is the protein shell that encases the viral genome.
DNA viruses generally have well-organized and symmetrical capsids, often with icosahedral symmetry (a 20-sided shape) due to the larger, more stable nature of their genomes.
DNA virus capsids are made of repetitive protein subunits that self-assemble into the capsid structure.
RNA viruses also possess capsids, but their capsids are often simpler and less symmetrical due to the smaller genome and the structural instability of RNA.
Many RNA viruses have helical symmetry, where the capsid proteins wrap around the RNA in a spiral fashion.
Like DNA viruses, RNA viruses also use repetitive protein subunits to build their capsids, but these are typically smaller and more flexible.

Viral Envelope

Some DNA viruses are enveloped, meaning they possess an outer lipid membrane derived from the host cell membrane, while others are non-enveloped.
The envelope plays a key role in viral entry by fusing with the host cell membrane.
Envelope proteins are essential for recognition and attachment to host cell receptors.
Many RNA viruses are also enveloped, though some are non-enveloped.
The envelope is particularly important for protecting the fragile RNA genome.
The viral envelope assists RNA viruses in attaching to host cells, typically through specific viral envelope glycoproteins that mediate entry.
The envelope also helps the virus avoid the host immune system.

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Description

Explore the fascinating world of viral genomes and capsid structures in this quiz. Learn about the differences between DNA and RNA viruses, their stability, and the symmetry of their protein shells. Test your knowledge on key features such as genome size and mutation rates.