Lecture 2 - Virus Classification

Question 1

What is the most difficult taxomic hierarchy to define for a virus and why?

Answer 1

Virus species are most difficult to classify because they do not breed.

Question 2

Describe polythetic hierarchical classification

Answer 2

Use of more than one property to describe the virus where no single property is essential.

Question 3

What are 4 properties used to classify viruses polythetically?

Answer 3

1) nature and sequence of nucleic acid in virion
2) symmetry of capsid
3) presence or absence of envelope
4) dimensions of virion and capsid

Question 4

Name the 2 virus families with dscDNA genomes

Answer 4

Hepadna

Papova

Question 5

Name the 3 virus families with dslDNA genomes

Answer 5

Adeno
herpes
pox

Question 6

Name the virus family with ssDNA genome

Answer 6

Parvo/circo

Question 7

Name the 4 virus families with +ssRNA genomes

Answer 7

Picorna (calici, astro)
Toga
Flavi
Corona

Question 8

Name the virus family with a diploid +ssRNA genome

Answer 8

Retro

Question 9

Name the 4 virus families with -ssRNA genomes

Answer 9

Rhabdo
paramyxo
filo
orthomyxo

Question 10

Name the virus family with an ambisense -ssRNA genome

Answer 10

Arena

Question 11

Name the virus family with a dsRNA genome

Answer 11

Reo

Question 12

Describe the following for Reoviruses:

1) family name derivation
2) virion morphology
3) genome structure
4) noteworthy features
5) species examples

Answer 12

1) respiratory enteric orphan
2) icosahedral, naked, triple-shelled capsids
3) segmented dsRNA
4) capsid structure and incomplete uncoating to subviral particles
5) reovirus, rotavirus

Question 13

Describe the following for Arenaviruses:

1) family name derivation
2) virion morphology
3) genome structure
4) noteworthy features
5) species examples

Answer 13

1) arenosus = sand (ribosomes inside virion)
2) helical, enveloped
3) -ssRNA in 2 segments
4) ambisense RNA: some genes encoded by genomic RNA others by complementary RNA
5) Lassa fever virus

Question 14

Describe the following for Orthomyxoviruses:

1) family name derivation
2) virion morphology
3) genome structure
4) noteworthy features
5) species examples

Answer 14

1) myxo = slime
2) helical, enveloped
3) segmented -ssRNA
4) segmented genome, requires nucleus (unusual for RNA viruses)
5) Influenza virus

Question 15

Describe the following for Filoviruses:

1) family name derivation
2) virion morphology
3) genome structure
4) noteworthy features
5) species examples

Answer 15

1) Filamentous
2) filamentous morphology is unusual, enveloped
3) -ssRNA, 19kb
4) agents of severe hemorrhagic fever in humans
5) ebolavirus

Question 16

Describe the following for Rhabdoviruses:

1) family name derivation
2) virion morphology
3) genome structure
4) noteworthy features
5) species examples

Answer 16

1) rhabdos = rod
2) helical, enveloped
3) -ssRNA
4) bullet shaped
5) rabies virus

Question 17

Describe the following for Paramyxoviruses:

1) family name derivation
2) virion morphology
3) genome structure
4) noteworthy features
5) species examples

Answer 17

1) myxo = slime, affinity for mucus
2) helical, enveloped
3) -ssRNA
4) often causes syncytia = cell fusion
5) measles, mumps, RSV

Question 18

Describe the following for Retroviruses:

1) family name derivation
2) virion morphology
3) genome structure
4) noteworthy features
5) species examples

Answer 18

1) retro = reverse transcribes RNA to DNA
2) enveloped, may or may not be icosahedral
3) diploid +ssRNA
4) diploid genome, reverse transcriptase, RNA tumor viruses
5) HIV

Question 19

Describe the following for Coronaviruses:

1) family name derivation
2) virion morphology
3) genome structure
4) noteworthy features
5) species examples

Answer 19

1) peplomers (spikes) form halo like sun’s corona
2) helical, enveloped
3) +ssRNA, largest RNA genome
4) large, petal-shaped peplomers, respiratory infections
5) SARS, MERS-CoV

Question 20

Describe the following for Flaviviruses:

1) family name derivation
2) virion morphology
3) genome structure
4) noteworthy features
5) species examples

Answer 20

1) Flavus = yellow (yellow fever virus)
2) Icosahedral, enveloped
3) +ssRNA
4) often arboviruses, polyprotein processing, often encephalitic or hemorrhagic
5) YFV, Dengue virus, Hepatitis C virus, Zika, West Nile Virus

Question 21

Describe the following for Togaviruses:

1) family name derivation
2) virion morphology
3) genome structure
4) noteworthy features
5) species examples

Answer 21

1) “wrapped” in envelope
2) Icosahedral, enveloped
3) +ssRNA
4) often arboviruses
5) rubella, semliki forest virus

Question 22

Describe the following for Picornaviruses (calici, astro):

1) family name derivation
2) virion morphology
3) genome structure
4) noteworthy features
5) species examples

Answer 22

1) pico = small, smallest RNA viruses
2) icosahedral, naked
3) +ssRNA
4) viral protein bound to 5’ end of genome, polyprotein processing
5) polio virus, rhinovirus, hep A virus

Question 23

Describe the following for Parvo/circoviruses:

1) family name derivation
2) virion morphology
3) genome structure
4) noteworthy features
5) species examples

Answer 23

1) smallest viruses
2) icosahedral, naked, + or - DNA
3) sscDNA, small genome, integrates in host DNA
4) some of the smallest known viruses
5) B19 virus (fifths disease), adeno-associated virus (gene therapy vector)

Question 24

Describe the following for Poxviruses:

1) family name derivation
2) virion morphology
3) genome structure
4) noteworthy features
5) species examples

Answer 24

1) pocks: vesicular skin lesions
2) complex capsid
3) dslDNA with covalently closed termini (unique)
4) largest animal viruses, replicate in cytoplasm
5) small pox (variola virus), vaccinia virus, molluscum contagiosum virus

Question 25

Describe the following for Herpesviruses:

1) family name derivation
2) virion morphology
3) genome structure
4) noteworthy features
5) species examples

Answer 25

1) herpein: to creep, nature of lesions
2) icosahedral, enveloped
3) dslDNA
4) latent and recurring infections, human tumors
5) herpes simplex, cytomegalovirus, Epstien-Barr virus, VZV

Question 26

Describe the following for Adenoviruses:

1) family name derivation
2) virion morphology
3) genome structure
4) noteworthy features
5) species examples

Answer 26

1) latent infection of adenoid tissues
2) icosahedral, naked
3) dslDNA
4) latent infections, cell transformation
5) human adenovirus (common cold)

Question 27

Describe the following for Papovaviruses:

1) family name derivation
2) virion morphology
3) genome structure
4) noteworthy features
5) species examples

Answer 27

1) Papilloma (warts), polyoma (many tumors), vacuolating (CPE in tissue culture)
2) icosahedral, naked
3) dscccDNA, minichromosome
4) cell transformation, tumor viruses
5) HPV, Merkel cell virus, simian virus 40

Question 28

Describe the following for Hepadnaviruses:

1) family name derivation
2) virion morphology
3) genome structure
4) noteworthy features
5) species examples

Answer 28

1) hepatitis, DNA
2) icosahedral, enveloped
3) dscDNA, nicked with large ss gap (unique)
4) serum hepatitis, persistent infections, liver cancer
5) hepatitis B virus

Question 29

Name the 12 enveloped virus families

ACFFHHOPPRRT

Answer 29

Arena, Corona, Filo, Flavi, Hepadna, Herpes, Orthomyxo, Paramyxo, Pox, Rhabdo, Retro, Toga.

Question 30

Name the 5 non-enveloped virus families

APPPR

Answer 30

Adeno, Papova, Parvo, Picorna, Reo