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Questions and Answers
What are the six basic stages in the life cycle of viruses?
Attachment, penetration (viral entry), uncoating, replication & translation, assembly, lysis.
What are the two main types of nucleic acids that classify viruses?
Only 8 herpesviruses are known to infect humans.
True
What is the Latin meaning of 'Parvovirus'?
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The genome size range of Rhabdoviruses is _____ kb.
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Which of the following diseases is caused by picornaviruses?
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What is the primary function of reverse transcriptase in retroviruses?
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Match the following families of viruses with their examples:
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All viruses are enveloped.
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What is indicated by the term 'icosahedral symmetry' in viruses?
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Study Notes
Classification and Nomenclature of Viruses
- The classification of viruses is based on whether the nucleic acid is DNA or RNA, whether the nucleic acid is single-stranded or double-stranded, whether the genome is segmented, the size of the virion, the symmetry of the capsid, and whether the virion is naked or enveloped.
Virus Genome Replication
- There are 6 basic stages in the life cycle of viruses: attachment, penetration (viral entry), uncoating, replication and translation, assembly, and lysis.
Herpesviruses (and other dsDNA viruses)
- Herpesviruses are double-stranded DNA viruses that affect mammals, birds, fish, reptiles, amphibians, and mollusks.
- There are over 100 herpesviruses that have been isolated from various hosts, but only 8 are known to affect humans.
- Herpesviruses can remain as persistent infections for the lifetime of the host and often reactivate especially if the host becomes immunocompromised.
Other dsDNA Viruses
- Other dsDNA viruses include Baculoviridae, Papillomaviridae, Polyomaviridae, and Poxviridae.
- Examples of dsDNA viruses include Autographa california nucleopolyhedrovirus, Human papillomaviruses, Simian virus, and Smallpox virus.
Parvoviruses (and other ssDNA viruses)
- Parvoviruses are the smallest known viruses with virion diameters ranging from 18-26 nm.
- Parvoviruses are single-stranded DNA viruses that infect vertebrates and invertebrates.
- Examples of ssDNA viruses include Porcine circovirus, Maize streak virus, and Phage φX174.
Reoviruses (and other dsRNA viruses)
- Reoviruses are double-stranded RNA viruses that infect a wide range of hosts including mammals, birds, plants, and insects.
- Examples of dsRNA viruses include Cypovirus, Orbivirus, Orthoreovirus, Phytoreovirus, Rotavirus, and Birnaviridae.
- The virion of most dsRNA viruses has icosahedral symmetry and are naked, except for the family Cystoviridae which is enveloped.
Picornaviruses (and other plus-strand RNA viruses)
- Picornaviruses are small RNA viruses with icosahedral symmetry and a diameter of 25-30 nm.
- Picornaviruses are plus-strand RNA viruses that function as mRNA once released into a host cell.
- Examples of plus-strand RNA viruses include Hepatitis A virus, Poliovirus, Coxsackieviruses, West Nile virus, SARS virus, and Rubella virus.
Rhabdoviruses (and other minus-strand RNA viruses)
- Rhabdoviruses are minus-strand RNA viruses with rod-shaped virions and a genome size of 11-15 kb.
- Examples of minus-strand RNA viruses include Vesicular stomatitis virus, Rabies virus, Influenza virus, Measles virus, and Ebola virus.
Retroviruses
- Retroviruses are RNA viruses that copy their genome into DNA during replication.
- Examples of retroviruses include Human Immunodeficiency Virus (HIV-1 and HIV-2), Rous sarcoma virus, and Murine leukaemia virus.
Hepadnaviruses and other reverse-transcribing DNA viruses
- Hepadnaviruses are DNA viruses that replicate via an RNA intermediate (reverse transcription).
- Examples of reverse-transcribing DNA viruses include Hepatitis B virus, Cauliflower mosaic virus, and Rice tungro bacilliform virus.
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Description
This quiz covers the classification and nomenclature of viruses, including virus genome replication and different types of viruses such as Herperviruses, Parvoviruses, and Retroviruses. Test your knowledge of virology!
