4 Virology

Question 1

what does it mean that viruses are obligate intracellular parasites?

Answer 1

• cannot live outside living cellular host
• cannot be treated or cured with existing medical therapies

Question 2

name 3 hosts for viruses

Answer 2

• plants (variegation)
• animals
• bacteria (bacteriophages

Question 3

how many cell types do viruses affect?

Answer 3

one specific cell type

Question 4

what are viroids?

Answer 4

• smallest known pathogens
• naked, circular, single-stranded RNA molecules that do not encode protein yet replicate autonomously when introduced to host plants

Question 5

a viral particle is a ____

Answer 5

viron

Question 6

viral structure consists of…

Answer 6

• protein coat
• nucleic acid core
• envelope (occasionally)

Question 7

what is the effect of a viral envelope?

Answer 7

steals plasma membrane from infected host cell, acting as camouflage from immune system

Question 8

name 3 ways to replicate viruses

Answer 8

• cell culture
• fertilized eggs
• living animals

Question 9

the protein coat surrounding the nucleic acid core is called a ____

Answer 9

capsid

Question 10

each capsid consists of identical protein units called ____

Answer 10

capsomeres

Question 11

what do capsomeres do to viral structure?

Answer 11

bond together and give capsid symmetry

Question 12

name 2 basic patterns of virus capsids

Answer 12

• helical symmetry
• icosahedral symmetry

Question 13

helical symmetry

Answer 13

protein subunits and nucleic acid are arranged in a helix

Question 14

icosahedral symmetry

Answer 14

protein subunits assemble into symmetrical shell that covers nucleic acid-containing core

Question 15

what are the 2 nucleic acid cores and forms by which viruses are characterized?

Answer 15

DNA and RNA
(double or single stranded)

Question 16

how many strands are in double stranded DNA?

Answer 16

4

Question 17

how many strands are in double stranded RNA?

Answer 17

2

Question 18

what are the 5 levels of viral classification?

Answer 18

• nucleic acid
• symmetry of capsid
• naked or enveloped
• type of nucleic acid
• family name

Question 19

what is the youngest viral family?

Answer 19

filoviridae

Question 20

how are hemorrhagic fevers classified?

Answer 20

(eg. Ebola, Marburg, Lassa)
- RNA
- helical
- enveloped
- single stranded
- filoviridae

Question 21

what is the largest viral family that infects humans?

Answer 21

herpes

Question 22

what is the most stable viral form?

Answer 22

viruses with double stranded DNA genome
(eg. herpesviridae)

Question 23

what viral form is most prone to mutation?

Answer 23

viruses with + single stranded genome
(eg. Ebola, HIV)

Question 24

many viruses that infect mammals are ____

Answer 24

enveloped

Question 25

all envelopes have a ____

Answer 25

phospholipid bilayer

Question 26

envelopes arise from...

Answer 26

plasma membrane of infected host cell

Question 27

lytic infections

Answer 27

host cell fills with virions and bursts resulting in cell death

Question 28

steps in lytic infection

Answer 28

- attachment - penetration - uncoating - biosynthesis - maturation - release

Question 29

virion attachment

Answer 29

- virus binds to specific receptors on host cell (viral tropism) - some require co-receptors for successful attachment

Question 30

virion penetration

Answer 30

- adhesion of virus to host receptors - engulfment into vesicle - viral RNA released from vesicle

Question 31

what is virion uncoating and what are 3 locations it can occur?

Answer 31

uncoating = removal of capsid - at plasma membrane - in cytoplasm - at nuclear membrane

Question 32

virion biosynthesis

Answer 32

develop provirus (partial host DNA + viral DNA)

Question 33

virion maturation

Answer 33

involves moving newly made virions to specific sites in cell for intracellular trafficking and assembly

Question 34

what is the most important part of virion assembly?

Answer 34

placement of viral genome inside the capsid

Question 35

virion assembly

Answer 35

- virion assembled while viral genome inside capsid - viral genome inserted into already-formed capsids