MIP: Introduction to Virology

Question 1

What does it mean that viruses are obligate intracellular parasites?

Answer 1

Viruses require intracellular environments, and often intracellular machinery to replicate

Question 2

What was the first human virus to be identified?

Answer 2

Yellow Fever

Question 3

What are the basic structural components of a virus?

Answer 3

Nucleic acids, a protein shell/capsid, and sometimes an envelope

Question 4

What are the 7 viral genome types?

Answer 4

ds DNA, ss DNA, ds RNA, ss + RNA, ss - RNA, ss + RNA to DNA, ds DNA w/ RNA intermediate

Question 5

What information is contained in the viral genome?

Answer 5

The information necessary to initiate and complete an infectious cycle

Question 6

What is a viral capsid and what is its function?

Answer 6

A protein coat surrounding the genome that maintain the virus and protects the nucleic acids

Question 7

What is a capsomer? A protomer?

Answer 7

Capsomers are the repeating protein subunits that make up the capsid and Protomers are the polypeptide chains which make up capsomers

Question 8

What are the simplest structures that can be built as a capsid?

Answer 8

Helical and icosahedral capsids

Question 9

What is a virion?

Answer 9

The complete virus particle

Question 10

What is a nucleocapsid? Nucleoprotein?

Answer 10

Nucleocapsids are capsid proteins assc. w/ viral genome; Nucleoproteins are proteins assc. w/ the viral genome that aren’t part of the capsid

Question 11

What is the difference between enveloped and naked viruses?

Answer 11

Enveloped viruses have capsids that are covered by host cell membrane

Question 12

How do viruses attach to their envelope?

Answer 12

Viral encoded protein “spikes”

Question 13

How are viruses classified? What is the most consistent classification based on?

Answer 13

Disease, mode of transmission, structure, and biochemical characteristics (latter 2 most consistent)

Question 14

What are the main characteristics of viruses that classifications are based on?

Answer 14

Type of genome, capsid symmetry, presence/absence of envelope, and size of genome and capsid

Question 15

What is a bacteriophage?

Answer 15

A virus that infects bacteria

Question 16

What is a viroid?

Answer 16

Infectious agents that consist solely of short strands of circular, ss RNA w/o a protein coat

Question 17

What is a prion?

Answer 17

An infectious agent comprised only of proteins w/o nucleic acids

Question 18

Where are prion proteins most abundantly found in the body?

Answer 18

The brain

Question 19

What are the most well-known human prion diseases?

Answer 19

Creutzfeldt-Jakob Disease (CJD), variant CJD, Gerstmann-Stausler-Scheinker Syndrome, Fatal Familial Insomnia, and Kuru

Question 20

What is the basis of Creutzfeldt-Jakob disease? What is the biggest risk factor?

Answer 20

Spontaneous transformation of normal proteins into prion proteins which allows for plaque formation; improperly sterilized surgical instruments

Question 21

What are the different events of the viral life cycle?

Answer 21

Attachment, Entry, Release of genome (uncoating), genomic replication, creation of new virus, release from cell

Question 22

How do viruses attach to cells?

Answer 22

Nonspecific electrostatic interactions as well as specific interactions with cell membrane proteins

Question 23

What are the two major mechanisms of viral entry into cells?

Answer 23

Non-endocytic route (enveloped viruses fuses with cellular membrane) and the endocytic route (clathrin-mediated endocytosis)

Question 24

What are the general differences between the replication of RNA and DNA viruses?

Answer 24

RNA viral replication occurs in the cell cytoplasm using virally encoded RNA-dependent RNA polymerase; DNA viral replication occurs in the nucleus and uses cell machinery

Question 25

True or False: Host cellular machinery is needed for viral assembly.

Answer 25

True

Question 26

What are the possible modes of transmission for viruses?

Answer 26

Blood, fecal-oral, respiratory, arthropod/zoonotic, mother to infant, urogenital, sexual contact, direct contact

Question 27

What is the difference between a localized and disseminated infection?

Answer 27

Localized infections have the same entry point and area of effect; disseminated viral infections may gain entry at one location but affect another

Question 28

What is viremia?

Answer 28

Presence of virus in the blood

Question 29

What are common characteristics shared by viruses transmitted via a fecal-oral route?

Answer 29

All naked viruses that are generally very resilient

Question 30

What are viral quasispecies?

Answer 30

A heterogeneous group of sequences clustering around a consensus

Question 31

What are zoonoses?

Answer 31

Virus introduced into new populations via animal or arthropod vector

Question 32

What is our best tool for controlling viral infections?

Answer 32

Prophylaxis

Question 33

What is viral virulence?

Answer 33

A quantitative statement of the degree or extent of pathogenesis (capacity of virus to cause disease in an infected host)

Question 34

What are the major mechanisms of viral pathogenesis?

Answer 34

Lytic infections kill the cell, and persistent infections do not cause cell death and may be chronic, latent, recurrent, or transforming

Question 35

What is syncytia?

Answer 35

Fusion of cells resulting in a large mass of cytoplasm containing several nuclei and is amechanism of viral cytopathogenesis

Question 36

What are viral inclusion bodies?

Answer 36

Distinctive abnormal structures in cells that are the result of viral infections