Exam 3 - Viruses

Question 1

What are viruses?

Answer 1

Non-living entities that can infect organisms of every domain

Question 2

Virus particle is called what?

Answer 2

Virion

Question 3

A virus’ structure is generally composed of what?

Answer 3

Nucleic acid surrounded by a protein coat

Question 4

The protein coat of a virus is called _______ and is composed of _______

Answer 4

Capsid; capsomeres

Question 5

T/F
Viral genome contains only a single type of nucleic acid (DNA/RNA) and NEVER both

Answer 5

True

Question 6

Two types of virions

Answer 6

Naked - sans envelope
Enveloped - surrounded by a lipid membrane

Question 7

Virion spike function

Answer 7

Attachment; allows virion to attach to host cell

Question 8

Virus shapes (3)

Answer 8

Isometric
Helical
Complex

Question 9

Isometric virus shape composed of:

Answer 9

flat surfaces forming equilateral triangles

Question 10

Helical virus shape composed of:

Answer 10

protein coat spirals around nucleic acid; rod-shaped appearance

Question 11

Complex virus shape composed of:

Answer 11

Isometric head with helical sheath/tail and other components

Question 12

The shape of a virus is determined by its:

Answer 12

Capsid

Question 13

Viral size is generally measured in:

Answer 13

nanometers

Question 14

T/F
Viruses can multiply outside metabolizing cells

Answer 14

False

Question 15

Viruses exist in two phases:

Answer 15

Extracellular
Intracellular

Question 16

Extracellular phase, the virus is:

Answer 16

Metabolically inert
Acts as basic chemicals

Question 17

Intracellular phase, the virus is:

Answer 17

metabolically active

Question 18

What viral cycle occurs when viruses multiply inside the cell; also termed productive cyle

Answer 18

Lytic cycle
»virus lyses infected cell (kills)

Question 19

What viral cycle occurs when the virus integrates into the host genome? also termed latent cycle

Answer 19

Lysogenic cycle

Question 20

Lytic Cycle steps (5)

Answer 20

Attachment
Penetration
Biosynythesis
Maturation
Release

Question 21

Attachment lytic step

Answer 21

Phage attaches baseplate to receptors and uses them for its own purpose (replication)

Question 22

Penetration lytic step

Answer 22

Entrance of virus OR nucleic acid into host cell

Question 23

Plant and bacteria viruses penetrate through the ____ _____ only

Answer 23

cell wall

Question 24

T/F
Animal viruses enter the cell through the cell wall only

Answer 24

False
Animal viruses enter the cell whole (no rigid cell wall)

Question 25

Penetration of the virus into animal cells is done through what process?

Answer 25

Phagocytosis; virus is engulfed by cell

Question 26

Biosynthesis lytic step

Answer 26

Duplication of viral components

Question 27

What 3 actions does the virus do during biosynthesis step?

Answer 27

Inhibit host DNA activity
Produce enzymes that destroy host DNA
Viral DNA takes over

Question 28

Early synthesized viral proteins are associated with

Answer 28

the replication of viral nucleic acids

Question 29

Late viral protein synthesization is associated with

Answer 29

the replication of other viral structures

Question 30

Maturation lytic step

Answer 30

assembly of the replicated viral components into a mature virus

Question 31

Release lytic step

Answer 31

Lysis of host cell;
releases viruses into environment
Virus is cloaked by host cell envelope

Question 32

Lysogenic Cycle

Answer 32

replication of a dormant virus; non-productive;integrates into host DNA

Question 33

Lysogenic cycle steps (4)

Answer 33

Attachment (same as lytic)
Penetration
Integration
Excised

Question 34

Lysogenic integration:

Answer 34

Viral nucleic acid incorporates into host chromosome and is hidden by repressor genes/proteins
Viral DNA replicated along with host cell

Question 35

Lysogenic Excision

Answer 35

Viral proteins repress host gene that would excise the provirus (virus integrated into host DNA),
but if host DNA is damaged;
host repair mechanisms destroy viral protein repressor;
allowing virus to excise from host DNA and return to lytic cycle

Question 36

Lysogenic Conversion

Answer 36

Prophage can express gene coding and cause organism to display new trait

Question 37

DNA Viruses replicate here

Answer 37

nucleus of host

Question 38

RNA Viruses replicate here; and by using

Answer 38

cytoplasm; RNA-dependent RNA polymerase

Question 39

ssRNA; + (sense) strand

Answer 39

Viral RNA serves as mRNA for protein synthesis and as a template for more viral RNA

Question 40

ssRNA; - (antisense) strand

Answer 40

Viral RNA is transcribed to a + strand to serve as mRNA for protein synthesis

Question 41

dsRNA

Answer 41

Contain both + and - strands
+ strand serves as mRNA

Question 42

Replication of retrovirus

Answer 42

uses reverse transcriptase to produce DNA from viral genome; alters host cell’s own DNA