Lecture 4: Viruses and Other Acellular Infectious Agents

Question 1

Bacterial viruses are called?

Answer 1

Bacteriophages

Question 2

Do archaeal have few or many viruses?

Answer 2

Few Archaeal Viruses

Question 3

True or False:

Most virions are eukarotic viruses.

Answer 3

True - plants, animals, protists, and fungi.

Question 4

What are virions classified into families based of?

Answer 4

• genome structure
• life cycle
• morphology
• genetic relatedness

Question 5

What are viruses classified by?

Answer 5

• Morphology
  
  • helical viruses
  • polyhedral viruses
  • enveloped viruses
  • complex viruses

Question 6

What are 2 examples of a helical virus?

Answer 6

• Rabies
• Ebola hemorrhagic fever

Question 7

What are 2 examples of a polyhedral virus?

Answer 7

• Adenovirus
• Poliovirus

Question 8

What is the largest animal virus?

Answer 8

poxviruses

Question 9

What do viruses attach to?

Answer 9

Cell Membrane

Question 10

How do viruses penetrate/enter the host cell?

Answer 10

endocytosis or fusion

Question 11

How are animal viruses released from the host cell?

Answer 11

By budding (enveloped viruses) or rupture.

Question 12

In the influenza virus, what is hemagglutinin required for?

Answer 12

In viral attachment to the host cell.

Question 13

What are the steps in animal virus multiplication?

Answer 13

1. Attachment to host cell
2. Penetration/Entry
3. Uncoating of genome
4. Biosynthesis
5. Maturation/Assembly
6. Release

Question 14

True or False:

Nonenveloped viruses lyse the host cell to escape.

Answer 14

True

Question 15

What is the special features of biosynthesis for ssDNA?

Answer 15

• Cellular enzyme transcribes viral DNA in nucleus.
• Virus Family -> parvoviridae

Question 16

What is the special features of biosynthesis for dsDNA?

Answer 16

• Cellular enzyme transcribes viral DNA in nucleus for herpesviridae and papovaviridae.
• Viral enzyme transcries viral DNA in virion, in cytoplasm for poxviridae.
• Virus Family ->
  
  • herpesviridae
  • papovaviridae
  • poxviridae

Question 17

What is the special features of biosynthesis for reverse transcriptase DNA?

Answer 17

• Cellular enzyme transcribes viral DNA in nucleus; reverse transcriptase copies mRNA to make viral DNA.
• Virus Family -> hepadnaviridae

Question 18

What is the special features of biosynthesis for + strand RNA?

Answer 18

• Viral RNA functions as a template for synthesis of RNA polymerase which copies – strand RNA to make mRNA in cytoplasm.
• Virus Family ->
  
  • picornaviridae
  • togaviridae

Question 19

What is the special features of biosynthesis for - strand RNA?

Answer 19

• Viral enzyme copies viral RNA to make mRNA in cytoplasm.
• Virus Family -> rhabdoviridae

Question 20

What is the special features of biosynthesis for dsRNA?

Answer 20

• Viral enzyme copies – strand RNA to make mRNA in cytoplasm.
• Virus Family -> reoviridae

Question 21

What is the special features of biosynthesis for reverse transcriptase RNA?

Answer 21

• Viral enzyme copies viral RNA to make DNA in cytoplasm; DNA moves to nucleus.
• Virus Family -> retroviridae