Concepts of Viruses

Question 1

Define virus

Answer 1

Infectious agent of small size
Multiply only in living cells of animals, plants, bacteria
Obligate parasites - metabolically inert when outside host
All rely on metabolic processes of host to reproduce
Viral disease = interaction b/w virus and host

Question 2

What does a mature virus particle consist of?

Answer 2

Central core of NA covered with protein rich coat

Question 3

What is required for viral reproduction?

Answer 3

Host cell + DNA or RNA

reproduce solely from their NA

Question 4

Why can’t a virus grow and multiply outside the host cell?

Answer 4

Lack metabolic activity = metabolically inert

Question 5

Does a virus have ribosomes?

Answer 5

No

viral genome is capable of utilizing normal cellular machinery for synthesis of viral components

Question 6

What are two ways a virus can manipulate the host cell?

Answer 6

1. integrate their DNA genome into the host genome

2. some lead to transformation of the host cell

Question 7

What are some important concepts generated from virus involvement?

Answer 7

1. Role of animal virus in understanding basic concepts of eukaryotic gene expression
2. Role of animal virus in recombinant DNA tech
3. Role of animal viruses in oncology
4. Vaccine development
5. Gene therapy

Question 8

Capsomere

Answer 8

individual protein of a capsid

Question 9

Capsid

Answer 9

protein shell that encloses the viral NA

Question 10

procapsid

Answer 10

capsid w/o viral genome

Question 11

core

Answer 11

central part of virus containing the genome

Question 12

Nucleocapsid

Answer 12

NA surrounded by capsid protein/s

genome + capsid

Question 13

Envelope

Answer 13

Bi-lipid membrane containing virus derived proteins enclosing the capsid
Not all viruses have one
Composed of proteins, lipids, and CHO
Some proteins from the host cell and some from the virus

Question 14

Peplomer

Answer 14

glycoprotein spike protruding from virus capsid.

Bind to specific receptors on a host cell

Question 15

Reverse transcriptase

What virus group has this?

Answer 15

enzyme that generates DNA from RNA template

Retroviruses

Question 16

Virion

Answer 16

Virus particle (virus is made up of different things… it is one component of the virus that can infect a host) – just the viral protein or just the genome

Question 17

What are the different capsid symmetry? Briefly explain

Answer 17

1. Icosahedral - polyhedron (20 faces)
2. Helical Symmetry - RNA has helical confirmation surrounded by protein capsid. Hollow center - like cylinder
3. Complex symmetry

Question 18

What are the complex symmetry components?

Answer 18

1. DNA vs. RNA
2. ss vs ds
3. • or + sense (RNA)
4. linear (DNA or RNA) vs circular (DNA)
5. single (DNA or RNA) vs segmented (RNA)

Question 19

What is the capsid symmetry for Filovirus, Adenovirus, and Poxvirus?

Answer 19

Filovirus - Helical
Adenovirus - Icosohedral
Poxvirus - complex symmetry

Question 20

What do virion proteins do?

Answer 20

Protect NA
Attach to receptors
Penetrate cell membrane
Replicate NA (some viruses)
Begin program for replication (some viruses)
Modify host cell (some viruses)

Question 21

T/F

All animal viruses with helical nucleocapsids are envoloped

Answer 21

True

Question 22

Briefly describe the composition of an influenza virus.

Answer 22

RNA virus
Envelope
Helical symmetry
Glycoprotein peplomers = hemagglutinin and neuraminidase

Question 23

What are the 9 basic virion properties used in taxonomy?

Answer 23

Morphology
Physiochemical and Physical properties
Genome
Proteins
Lipids
CHO
Genome organization and replication
Antigenic properties
Biologic properties

Question 24

T/F

All nonenveloped viruses are Icosohedral

Answer 24

True

Question 25

What is the benefit or disadvantage of an enveloped virus?

Answer 25

Envelope viruses do not survive in the environment as long as non-enveloped viruses

Non-enveloped viruses are very resistant to environmental conditions!

Question 26

What are the viruses with ssDNA?

Answer 26

Circoviridae

Parvoviridae

Question 27

What is a positive sense virus? What are they carrying that makes them unique?

Answer 27

When RNA is close in composition to mRNA so it can readily make protein directly
Contain a starting point within their genome to start production of protein assembly (AUG segment)

Question 28

What is unique about negative sense RNA viruses?

Answer 28

They carry a RNA - dependent polymerase with them in their outer protein for production of + template RNA strand when assembling new virus

Question 29

Which is infectious vs. non-infectious, positive sense and negative sense?

Answer 29

Positive sense = infectious

Negative sense = non-infectious