General Virology 1

Question 1

What is a virus?

Answer 1

A filterable agent, a small obligate intracellular “parasite” that is inert outside of host cells.

Question 2

Can viruses have RNA and DNA genomes?

Answer 2

NO! One or the other

Question 3

Propagation of viruses depends on what?

Answer 3

The specialized host cells that supply the metabolic and biosynthetic machinery of prokaryotic and eukaryotic cells

Question 4

Do viruses have functional ribosomes?

Answer 4

No they steal ribosomes from other cells (same with other organelles)

Question 5

Name 3 difference between bacteria and viruses

Answer 5

Question 6

Example of virus that internalizes ribosomes

Answer 6

Arenavirus

Question 7

Can you see virus with a light microscope?

Answer 7

No, need electron microscope or Nanoscopy

Question 8

Size range of viruses

Answer 8

17 nm (circovirus) to 250 nm (small pox)

Question 9

What are the two forms of viruses?

Answer 9

Naked and enveloped

Question 10

Describe a Naked virus

Answer 10

A genome (DNA or RNA) protected by a capsid (capsid is 100% protein)

-May have spike proteins

Question 11

what is a nucleocapsid?

Answer 11

The capsid and genome

Question 12

Function of the capsid?

Answer 12

Acts as a shell to protect the viral genome from nucleases

Question 13

Describe enveloped viruses

Answer 13

A host derived lipid bilayer, that closely surrounds the viral capsid and genome. The exterior of the bilayer is studded with glycosylated (trans-) membrane proteins

Question 14

Why are glycosylated proteins important?

Answer 14

They help determine what hosts the virus can invade and antigenic composition of the virus

Question 15

Budding viruses contain what?

Answer 15

They carry host cells proteins that are integral constants of their viral envelope (Why not easily detected by immune system)

Question 16

Which virus type more vulnerable to soap?

Answer 16

Envelope b/c made of lipid bilayer that soap breaks down (naked virus needs stronger cleaners)

Question 17

What is the largest virus?

Answer 17

Pithovirus (only infects amoebas)
Mimivirus and pandora virus are also large

pandora virus has the largest genome

Question 18

What is the largest animal virus?

Answer 18

Poxviruses

Question 19

What is the smallest viruses?

Answer 19

Circoviruses (makes only 2 proteins)

Question 20

What is a bacteriophage? Describe its structure

Answer 20

A virus that infects and replicates within bacteria and archaea

Has a head which contains protein and DNA and a tail that contains only proteins

Question 21

Name the 6 viral shapes and give an example of each

Answer 21

1) Elongated- E.coli
2) Dumbell- pox. virus
3) Crown like- covid viruses (enveloped)
4) Bullet shape- Rabies
5) Rotovirus
6) Naked- Adenovirus

Question 22

What is the implication of having a segmented genome in a virus?

Answer 22

Because little segments can get packed up into different viruses and replicate. They reassort into new strains (1 and 2 can combine to make 3) These new strains that can evade the immune system. This is called reassortment. It causes the Spanish influenza, (has swine human and avian origin)

Question 23

Name basic steps and enzymes involved in the central dogma

Answer 23

Question 24

Name the two classification systems for viruses

Answer 24

International Committee on Taxonomy on Viruses (ICTV)

Baltimore Classification

Question 25

Describe the ICTV classification system

Answer 25

Viruses classified on order, family, subfamily, genus and species Not phylum or class since their small genome size and mutation rate make it difficult to determine ancestry beyond order

Question 26

What are virus suffixes for order, family, subfamily, genus and species

Answer 26

Order: -virales Family: -viridae Subfamily: -virinae Genus: -virus Species: -virus

Question 27

How many orders are there in the ICTV system?

Answer 27

7

Question 28

Name the 7 ICTV classes and characteristics about them

Answer 28

1) Caudovirales- tailed dsDNA bacteriophages (does not infect animals) 2) Herpesvirales-large eukaryotic dsDNA viruses 3) Ligamenvirales-linear, dsDNA, archaean viruses (does not infect animals) 4) Mononegavirales-nonsegmented (-) strand ssRNA, plant and animal viruses 5) Nidovirales- (+) strand ssRNA, vertebrate viruses 6) Picornavirales-small (+) strand ssRNA viruses that infect a variety of plant, insect and animal hosts 7) Tymovirales-monopartite (+) ssRNA viruses that infect plants (does not infect animals)

Question 29

Describe the Baltimore classification system

Answer 29

Used in conjunction with ICTV and is based on the mechanism of mRNA production (transcription), different mechanisms are used to achieve each family

Question 30

How many groups are there in the Baltimore system?

Answer 30

7

Question 31

What are the 7 Baltimore groups and their descriptors?

Answer 31

I: dsDNA viruses (e.g. Adeno, Herpes, Pox) II: ssDNA viruses (+ sense) DNA (e.g. Parvoviruses) III: dsRNA viruses (e.g. Reoviruses) IV: (+)ssRNA viruses (e.g. Picornaviruses, Togaviruses) V: (−)ssRNA viruses (e.g. Orthomyxoviruses, Rhabdoviruses) VI: ssRNA-RT viruses (+ sense) RNA with DNA intermediate in life-cycle (e.g. Retroviruses) VII: dsDNA-RT viruses (e.g. Hepadnaviruses)

Question 32

What does the + or - mean?

Answer 32

Defines the polarity compared to mRNA, which defines how they are translated by ribosomes + ssRNA use their own viral RNA genome as mRNA -ssRNA uses RNA dependant RNA polymerase from the viron

Question 33

Give an example of a group 1 virus

Answer 33

dsDNA viruses e.g. Adeno, Herpes, Pox

Question 34

Give an example of a group 2 virus

Answer 34

ssDNA viruses (+ sense) DNA e.g. Parvoviruses

Question 35

Give an example of a group 3 virus

Answer 35

dsRNA viruses e.g. Reoviruses

Question 36

Give an example of a group 4 virus

Answer 36

(+)ssRNA viruses e.g. Picornaviruses, Togaviruses

Question 37

Give an example of a group 5 virus

Answer 37

(−)ssRNA viruses (e.g. Orthomyxoviruses, Rhabdoviruses)

Question 38

Give an example of a group 6 virus

Answer 38

ssRNA-RT viruses (+ sense) RNA with DNA intermediate in life-cycle (e.g. Retroviruses)

Question 39

Give an example of a group 7 virus

Answer 39

dsDNA-RT viruses (e.g. Hepadnaviruses)

Question 40

Example of DNA envoloped virus

Answer 40

Poxviradae (pox viruses)

Question 41

Example of DNA naked virus

Answer 41

Parvovirade (parvo viruses)

Question 42

Example of enveloped RNA virus

Answer 42

Influenza Virus Cornaviradae

Question 43

Example of naked RNA virus

Answer 43

Reoviridae (rotavirus)

Question 44

70% of viruses are what?

Answer 44

RNA viruses