Virology Basics: DNA vs RNA Viruses

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Questions and Answers

What did Stanley and Bawden contribute to the understanding of viruses in the 1930s?

They proposed that all viruses have RNA genomes.

They discovered the DNA composition of all viruses.

They identified viruses as solely protein structures.

They established the ribonucleoprotein nature of viruses. (correct)

What is the primary goal of a virus according to Darwinian principles?

To survive outside of a host cell.

To reproduce effectively. (correct)

To evolve into more complex organisms.

To cause diseases in hosts.

Which virus is an example of a positive single-stranded RNA virus?

HIV-1

Herpes simplex virus

SARS-CoV-2 (correct)

Parvovirus

Which of the following types of genomes can be found in viruses?

Single and double-stranded RNA and DNA Signup and view all the answers

What does the phrase 'bad news wrapped up in protein' suggest about viruses?

The genetic information within viruses is encapsulated by a protein shell. Signup and view all the answers

Which component distinguishes RNA from DNA at the 2' ribose position?

RNA has an OH at the 2' position while DNA has an H Signup and view all the answers

What is the typical structural form of DNA compared to RNA?

DNA is double stranded while RNA is single stranded Signup and view all the answers

Which type of nucleic acid is generally associated with long-term storage?

DNA is associated with long-term storage Signup and view all the answers

What is the primary role of polymerase fidelity in RNA compared to DNA?

DNA has higher polymerase fidelity than RNA Signup and view all the answers

Which statement best describes positive mutations in viral populations?

They can drive positive selection that enhances viral fitness Signup and view all the answers

In the context of antigenic drift, what is primarily accumulated over time?

Subtle mutations in antigens Signup and view all the answers

What drives viral genetic heterogenicity according to selective pressure?

Mutation rate and viral fitness drive selection Signup and view all the answers

Which of the following statements about RNA and DNA is true regarding their usage of bases?

DNA uses thymine while RNA utilizes uracil Signup and view all the answers

Which mutation is associated with an increased binding affinity for the ACE2 receptor?

Y453F Signup and view all the answers

What effect does the Δ69–70 mutation have on the SARS-CoV-2 virus?

Altered conformation of an exposed NTD loop Signup and view all the answers

Which of the following mutations is identified as an escape mutation during exposure to certain monoclonal antibodies?

E484K Signup and view all the answers

What percentage of plasma or serum neutralizing antibodies target the spike receptor-binding domain after vaccination?

90% Signup and view all the answers

Which of the following mutations completely abolishes neutralization?

N5 insertion Signup and view all the answers

What is the characteristic feature of segmented viruses?

Divided genes across two or more molecules of RNA/DNA Signup and view all the answers

S477G mutation displayed resistance in how many sera tested?

Two Signup and view all the answers

Which of the following is NOT a common mutation associated with escape from neutralization?

N148A Signup and view all the answers

What is antigenic shift primarily characterized by?

Major alteration in antigen sequence Signup and view all the answers

How does recombination contribute to viral evolution?

It allows acquisition of new proteins Signup and view all the answers

What is a major factor that increases recombination frequency in RNA viruses?

Discontinuous replication mechanism Signup and view all the answers

What is one method by which viruses can evade the immune system?

By utilizing viral mimics to confuse immune receptors Signup and view all the answers

What role does the CMV UL18 protein play in immune evasion?

Inhibits interaction with natural killer receptors Signup and view all the answers

Which type of virus is most likely to have large genomes that facilitate immune system evasion?

Double-stranded DNA viruses Signup and view all the answers

How does genome reassortment influence antigenic shift?

By facilitating major alterations in antigen sequence Signup and view all the answers

What is the difference between homologous and non-homologous recombination?

Homologous recombination involves similar sequences, non-homologous does not. Signup and view all the answers

What characteristic of RNA viruses contributes to their rapid adaptation?

Higher mutation rates Signup and view all the answers

What is a significant clinical consequence of viral latency?

Persistent infections Signup and view all the answers

Which of the following features distinguishes dsDNA viruses from RNA viruses?

Greater storage capacity Signup and view all the answers

What challenges are posed by the presence of ectopic DNA in the nucleus?

It cannot be distinguished from endogenous DNA. Signup and view all the answers

Which feature of RNA viruses supports their plasticity and adaptability?

Segmented genomes Signup and view all the answers

What is a primary reason dsDNA viruses are more difficult to detect in the nucleus?

They have stable and integrated genomes. Signup and view all the answers

What is a consequence of the absence of antigen presentation during viral latency?

Lack of immune response to infected cells Signup and view all the answers

Which of the following statements about RNA viruses is true?

They have higher mutation rates than DNA viruses. Signup and view all the answers

Study Notes

Viral Genomes: DNA vs RNA

Viruses can have either DNA or RNA genomes.
RNA viruses evolve faster than DNA viruses resulting in rapid adaptation.
RNA viruses' genomes are more plastic, potentially increasing coding capacity through segmentation and polyproteins.
DNA viruses have greater storage capacity and broader protein arsenals.
DNA viruses, being more stable, are harder to identify within the nucleus often causing persistent infections via latency.

Origin of Virology

Virology, the study of viruses, began in 1879 with an agricultural catastrophe.
Martinus Beijerinck demonstrated that tobacco mosaic disease was caused by a virus in 1899.
Viruses were initially considered poisons, secreted from snakes, creatures, and plants.

Virus Structure

Early scientists discovered that viruses were comprised of proteins and nucleic acids (Stanley, 1935, Bawden, 1936).
The viral nucleic acid is surrounded by a capsid (protein shell).
Viruses have a protein subunit that creates the capsid surrounding their nucleic acid.

Viral Replication and Evolution

Viruses replicate by infecting host cells and using the host machinery (i.e., proteins and ribosomes) to produce more viral components.
The Darwinian goal for a virus is to reproduce.
Viruses have different genomic structures which differ in their stability.
Mutations in viruses and viral replication mechanisms are key factors in evolution.
Viral genetic heterogenicity depends on mutation rate, with most mutations having no effect on selective pressure.
Negative mutations are usually eliminated.
Positive mutations can change mutation rate.

Types of Viral Genomes

RNA viruses with single-stranded positive sense RNA are present in many viruses (e.g., SARS-CoV-2, HIV-1).
RNA viruses with negative-strand RNA (e.g., Influenza) are present
DNA viruses have double-stranded DNA, single stranded, or single-stranded negative-sense RNA (e.g., Parvovirus).

Molecular Differences of RNA and DNA

RNA uses uracil instead of thymine in its nucleic acid structure.
RNA is typically single-stranded, while DNA is typically double-stranded.
RNA is found in the cytoplasm and nucleus, while DNA is mainly found in the nucleus.
RNA has a hydroxyl group at the 2' carbon of the sugar-phosphate backbone. DNA does not.
DNA tends to be more stable than RNA since its structure prevents degradation.

Viral Mimicry

Viruses can mimic host signals to avoid detection by the immune system.
The virus can mimic the host's receptor to "steal" resources and disable the immune response.

Genomic diversification

Recombination allows for major changes, acquiring new or altered genes that can lead to antigenic shift.
Recombination can happen during replication, disrupting a viral sequence and causing hybrid new strains.
Homologous recombination and non-homologous end joining are processes involved in genomic diversification.

Viral latency

The lack of viral antigens allows for prolonged infections through prolonged latency, causing recurrent infections.

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Description

This quiz explores the foundational concepts of virology, focusing on the differences between DNA and RNA viruses. Learn about their structures, origins, and evolutionary adaptations. Test your knowledge on the key features that distinguish these two types of viral genomes.