Virus Structure and Classification

Question 1

Give the definition of a virus in 4 words or less.

Answer 1

A capsid-encoding organism

Question 2

Which are “filterable agents”: bacteria or viruses?

Answer 2

Viruses, because they can pass through a 220nm-pores filter

Question 3

What does it mean that viruses are “obligate intracellular parasites”?

Answer 3

They can only replicate inside cells

Question 4

What is the difference between a virion and a virus?

Answer 4

A virus is the whole organism, with all its proteins and replicative abilities, that takes over a host cell. A virion is just the viral genome and capsid.

Question 5

Name the 3 basic gene modules shared by all viruses.

Answer 5

The viral genome codes for: capsid, replicon, and host cell interacting factors

Question 6

Which viral proteins are structural and which are non-structural? What does this mean?

Answer 6

Capsid proteins are structural and host cell interacting factors are non-structural, meaning that capsids are always part of the virion while host interacting factors never are.
(Replicon genes may be either structural or non-structural)

Question 7

How is the shape of a virus’s capsid related to its genome type?

Answer 7

They are not related. Capsid shape and genome type are independent.

Question 8

What structure characterizes an enveloped virion vs. a naked virion? How does the enveloped virion obtain this structure?

Answer 8

An enveloped virion has a lipid bilayer which it takes from the host cell’s membrane or organelle membranes

Question 9

List the 3 factors on which virus classification is based.

Answer 9

Host cell, genome type, and virion structure

Question 10

What is a virus’s nucleocapsid?

Answer 10

Just means the capsid or core

Question 11

Give 2 terms that refer to the jelly-like layer of proteins that surrounds the capsid in some viruses.

Answer 11

Tegument or matrix

Question 12

Give the capsid shape, genome type, and enveloped/naked status for adenovirus.

Answer 12

Icosahedral, dsDNA, naked

Question 13

Give the capsid shape, genome type, and enveloped/naked status for poxvirus.

Answer 13

Complex, dsDNA (with sealed ends), enveloped

Question 14

Give the capsid shape, genome type, and enveloped/naked status for influenza virus.

Answer 14

Helical, segmented (-) RNA, enveloped

Question 15

Give the capsid shape, genome type, and enveloped/naked status for HIV retrovirus.

Answer 15

Icosahedral, (+) ssRNA, enveloped

Question 16

Give the capsid shape, genome type, and enveloped/naked status for herpesvirus.

Answer 16

Icosahedral, dsDNA, enveloped

Question 17

List in order from smallest to largest: ribosome, bacterium, naked virion, nucleus

Answer 17

Ribosome - Virion - Bacterium - Nucleus

Question 18

Which of the example viruses is naked: adenovirus, poxvirus, influenza, retrovirus, and herpesvirus.

Answer 18

Only adenovirus is not enveloped

Question 19

Which of the example viruses have double-stranded DNA: adenovirus, poxvirus, influenza, retrovirus, and herpesvirus.

Answer 19

Adenovirus, poxvirus, and herpesvirus

Question 20

Which of the example viruses are helical: adenovirus, poxvirus, influenza, retrovirus, and herpesvirus.

Answer 20

Influenza virus

Question 21

State the 3 unifying principles of virology.

Answer 21

1. The genome encodes a capsid.
2. The virus infects a cell, survives, replicates, and assembles virions.
3. The virion is transmitted to a new host.