Viruses

Question 1

What is a virus?

Answer 1

Minuscule, acellular infectious agent having either DNA or RNA

Question 2

What is the cause of most of the diseases that plague the industrialized world?

Answer 2

Viruses

Question 3

When the virus exists in an extracellular state, what is it called?

Answer 3

Virion

Question 4

What is the name of the virus’s protein coat that surrounds the nucleic acid core?

Answer 4

Capsid

Question 5

The capsid together with the nucleic acid core is called what?

Answer 5

Nucleocapsid

Question 6

What is the outer structure of the virus that encloses the nucleocapsids of some other viruses?

Answer 6

Phospholipid envelope

Question 7

What is the purpose of the phospholipid envelope of viruses?

Answer 7

Provide protection for viral nucleic acid and means of attachment to host cells

Question 8

Once in the intracellular state, what happens to the virus structure?

Answer 8

Uncoating occurs and the capsid is removed leaving the virus to exist simply as nucleic acid

Question 9

What kind of virus only infects a particular kind of cell in a particular host? (Ex. = HIV infecting helper T cells)

Answer 9

Specific

Question 10

What kind of virus can infect many kinds of cells in many different hosts?

Answer 10

Generalists

Question 11

What types of organisms are susceptible to some sort of viral attack?

Answer 11

ALL types (even other viruses!)

Question 12

What virus is a classic example of a “bullet-shaped” virus?

Answer 12

Rabies

Question 13

What is the most common viral shape?

Answer 13

Icosahedron (20 sided dome)

Question 14

What is the shape of a polyhedral virus?

Answer 14

Geodesic dome

Question 15

What is the shape of a helical virus?

Answer 15

Spiral

Question 16

What is the shape of a complex virus?

Answer 16

Capsids of many shapes

Question 17

What is a bacteriophage?

Answer 17

A virus that attacks bacteria

Question 18

How is the viral envelope of a virus obtained?

Answer 18

Acquired from host cell during viral replication or release

Question 19

What are the viral glycoproteins that project on the viral envelope called?

Answer 19

Spikes

Question 20

What is the purpose of the viral envelope?

Answer 20

Provides protection, plays role in host recognition, and helps viruses enter host cells

Question 21

What is lytic replication?

Answer 21

Replication cycle usually resulting in death and lysis of host cell

Question 22

What is lysogeny?

Answer 22

Modified replication cycle where infected host cells grow and reproduce normally for generations before they lyse

Question 23

What are the inactive phages called during lysogeny?

Answer 23

Prophages

Question 24

What is lysogenic conversion?

Answer 24

When phages carry genes that alter the phenotype of a bacterium that can change it from being harmless to a pathogen

Question 25

Why is viral replication different in animal cells?

Answer 25

Presence of envelope, eukaryotic nature of cells, and lack of cell wall

Question 26

Replication of animal viruses is guided by what?

Answer 26

Chemical attraction

Question 27

What are the attachment molecules that mediate attachment for animal viruses?

Answer 27

Glycoprotein spikes

Question 28

What are the three mechanisms of entry of animal viruses?

Answer 28

Direct penetration, membrane fusion, and endocytosis

Question 29

What are latent viruses or proviruses?

Answer 29

Animal viruses that remain dormant in host cells

Question 30

What is the inexpensive way to culture viruses in the laboratory?

Answer 30

In embryonated chicken eggs

Question 31

What is a prion?

Answer 31

Proteinaceous infectious agent that lacks nucleic acid

Question 32

Where is cellular PrP protein found, and what does it look like?

Answer 32

Made by all mammals and is a normal structure with alpha-helices

Question 33

What is a prion PrP?

Answer 33

Disease-causing form with beta-sheets

Question 34

How can prions be destroyed?

Answer 34

Incineration or autoclaving in sodium hydroxide

Question 35

What does prion PrP do to cellular PrP?

Answer 35

Converts it into prion PrP by inducing conformational change

Question 36

In what body system is prion expression most predominant?

Answer 36

Nervous system (possible elsewhere, however)

Question 37

What are prion diseases in the nervous system?

Answer 37

Formation of large vacuoles in the brain that are characteristically spongy in appearance

Question 38

What are examples of spongiform encephalopathies?

Answer 38

BSE, vCJD, Kuru

Question 39

Prions composed of different proteins may lie behind what other muscular and neuronal degenerative diseases?

Answer 39

Alzheimer's disease, Parkinson's disease, and ALS