Chapter 15: DNA/RNA Viruses Classification

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Questions and Answers

What are the two groups of DNA?

dsDNA or ssDNA

Is dsDNA enveloped or nonenveloped?

Nonenveloped

Can be either (correct)

Neither

Enveloped

Is ssDNA enveloped or nonenveloped?

Nonenveloped (correct)

Enveloped

Neither

Can be either

What virus families are found in nonenveloped dsDNA?

Adenoviridae and Papillomaviridae Signup and view all the answers

What virus families are found in enveloped dsDNA?

Poxviridae, Herpesviridae, and Hepadnaviridae Signup and view all the answers

What virus families are found in nonenveloped ssDNA?

Parvoviridae Signup and view all the answers

What are the two groups of RNA?

ssRNA or dsRNA Signup and view all the answers

Is ssRNA positive sense or negative sense?

Can be either Signup and view all the answers

Is positive sense ssRNA, nonenveloped or enveloped?

Can be either Signup and view all the answers

What is the meaning of positive sense ssRNA viruses?

They act as mRNA. Signup and view all the answers

What virus families are in positive sense, nonenveloped, ssRNA?

Picornaviridae and Caliciviridae Signup and view all the answers

What virus families are in positive sense, enveloped, ssRNA?

Coronaviridae, Retroviridae, Flaviviridae, and Togaviridae Signup and view all the answers

What is the meaning of negative sense ssRNA?

They are complementary base to the mRNA. Signup and view all the answers

Are negative sense ssRNA, enveloped or nonenveloped?

Enveloped Signup and view all the answers

What virus families are found in negative sense, enveloped, ssRNA?

Filoviridae, Orthomyxoviridae, Paramyxoviridae, Arenaviridae, and Bunyaviridae Signup and view all the answers

Is dsRNA positive sense or negative sense?

Neither Signup and view all the answers

Is dsRNA enveloped or nonenveloped?

Nonenveloped Signup and view all the answers

What virus family is found in nonenveloped dsRNA?

Reoviridae Signup and view all the answers

Which is smaller, the genome of RNA viruses or the genome of DNA viruses?

RNA viruses Signup and view all the answers

What does the genome of RNA heavily depend on?

Host cell's proteins and enzymes for replication Signup and view all the answers

Why is the genome of RNA more prone to errors (mutations)?

RNA polymerase lacks proofreading ability. Signup and view all the answers

What are retroviruses?

Viruses that replicate indirectly through a DNA intermediate. Signup and view all the answers

What are DNA viruses?

Viruses that replicate in the host cell. Signup and view all the answers

What are RNA viruses?

Viruses that replicate in the host cell ribosomes. Signup and view all the answers

Study Notes

DNA Classification

DNA viruses are categorized into two groups: double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA).
dsDNA can be either enveloped or nonenveloped, while ssDNA is exclusively nonenveloped.

Nonenveloped DNA Virus Families

Nonenveloped dsDNA families include Adenoviridae (associated with common colds and viral meningitis) and Papillomaviridae (linked to warts and cervical cancer).
The only known family in nonenveloped ssDNA is Parvoviridae, which causes fifth disease and gastroenteritis.

Enveloped DNA Virus Families

Enveloped dsDNA families are:
- Poxviridae (responsible for smallpox)
- Herpesviridae (causes cold sores, chicken pox, shingles, mononucleosis)
- Hepadnaviridae (includes Hepatitis B and associated liver cancer)

RNA Classification

RNA viruses are divided into two types: single-stranded RNA (ssRNA) and double-stranded RNA (dsRNA).
ssRNA can be classified further into positive-sense and negative-sense.

Positive-Sense ssRNA Characteristics

Positive-sense ssRNA can be either enveloped or nonenveloped and functions as mRNA, enabling direct translation by host ribosomes.
Families under positive-sense, nonenveloped ssRNA include:
- Picornaviridae (causes the common cold, hepatitis A, polio)
- Caliciviridae (causes gastroenteritis)
Enveloped positive-sense ssRNA families consist of:
- Coronaviridae (includes SARS)
- Retroviridae (includes HIV)
- Flaviviridae (includes yellow fever, dengue fever, Zika virus, West Nile fever, hepatitis C)
- Togaviridae (includes rubella and encephalitis)

Negative-Sense ssRNA Characteristics

Negative-sense ssRNA is enveloped and is complementary to mRNA, meaning it must be converted to positive-sense RNA by RNA polymerase before translation can occur.
Families of negative-sense, enveloped ssRNA viruses include:
- Filoviridae (causes Ebola and Marburg disease)
- Orthomyxoviridae (causes influenza)
- Paramyxoviridae (includes mumps and measles)
- Arenaviridae (associated with Lassa fever)
- Bunyaviridae (associated with hantavirus pulmonary syndrome)
- Rhabdoviridae (associated with rabies)

Additional RNA Information

dsRNA is neither classified as positive nor negative sense and is always nonenveloped.
The only known family of dsRNA viruses is Reoviridae, linked to gastroenteritis.

Genome Characteristics and Mutations

RNA virus genomes are generally smaller than DNA virus genomes.
RNA viruses rely heavily on host cell proteins and enzymes for replication.
Higher mutation rates in RNA viruses stem from RNA polymerase's lack of proofreading ability, leading to rapid emergence of new strains.

Retrovirus Definition

Retroviruses utilize reverse transcriptase to replicate indirectly through a DNA intermediate, producing dsDNA from an ssRNA genome.

Replication Processes

DNA viruses replicate within the host cell, while RNA viruses replicate at the host cell ribosomes.

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Description

Explore the classification of DNA and RNA viruses with this quiz. You'll learn about different types of DNA, including dsDNA and ssDNA, and their characteristics. Test your knowledge on enveloped and nonenveloped viruses, as well as various virus families related to dsDNA.