Ch.8 Viruses

Question 1

genetic element that cannot replicate independently of a living (host) cell

Answer 1

Virus

Question 2

extracellular form of a virus

exists outside host and facilitates transmission from one host cell to another

Answer 2

virion

Question 3

with a virus when does replication and reproduction happen?

Answer 3

only upon infection meaning entry into host cell

Question 4

how can viruses be classified?

Answer 4

on the basis of the hosts they infect, genetics and structure

Question 5

structure of a virus consists of ?

Answer 5

Capsid
nucelocapsid
envelope

Question 6

the protein shell that surrounds the genome of a virus particle, composed of capsomeres

Answer 6

capsid

Question 7

how can capsids be put together

Answer 7

through self-assembly (spontaneous) or require host cell folding assistance.

Question 8

nucleic acid + protein

Answer 8

Nucleocapsid:

Question 9

: phospholipid bilayer acquired from host membranes

Answer 9

Envelope

Question 10

most bacterial viruses consist of what kind of virus and what is it composed of ?

Answer 10

naked viruses

composed of nucleocapsids (nucelic acid and capsid) only

Question 11

many animal viruses consist of what kind of virus ?

Answer 11

Enveloped viruses (nucleocapsid + envelope)

Question 12

human papillomavirus is associated with what kind of viral symmetry

Answer 12

icosahedral: spherical viruses

Question 13

this symmetry is common to bacteriophages

Answer 13

complex

Question 14

name all the structures the compose the viral genome

Answer 14

either DNA or RNA genomes
single-stranded or double-stranded
either linear or circular

Question 15

plus sense (same as mRNA) or 
minus sense (complementary to mRNA)
is associated with single stranded or double stranded dna/rna

Answer 15

single stranded

Question 16

RNA viruses that convert between RNA and DNA are called

Answer 16

family Retroviridiae(ssRNA) and Hepadnaviridae(dsDNA)

Question 17

This enzyme makes hole in cell wall to allow nucleic acid entry
also lyses bacterial cell to release new virions

Answer 17

lysozyme

Question 18

destroy glycoproteins and glycolipids

qllows liberation of viruses from cell

Answer 18

neuraminidases

Question 19

RNA-dependent RNA polymerases

Answer 19

RNA replicases

Question 20

RNA-dependent DNA polymerase in retroviruses

Answer 20

Reverse transcriptase

Question 21

Viral activities

replicates and destroys host?

Answer 21

lytic infection

Question 22

Viral activities

host cell genetically altered because viral genome becomes part of host genome?

Answer 22

lysogenic (latent) infection

Question 23

viral DNA

Answer 23

prophage

Question 24

Phases of viral replication in a permissive (supportive) host

Answer 24

attachment (adsorption) of the virion
penetration (entry, injection) of the virion nucleic acid
synthesis of virus nucleic acid and protein by host cell metabolism as redirected by virus
assembly of capsids and packaging of viral genomes into new virions
release of mature virions from host cell

Question 25

Viral Entry and Uncoating | Three methods used:

Answer 25

1. fusion of the viral envelope with host membrane; nucleocapsid enters 2. endocytosis in vesicle; endosome aids in viral uncoating 3. injection of nucleic acid

Question 26

in the one step growth curve when does increase occur?

Answer 26

when the cell bursts

Question 27

what happens during the eclipse stage

Answer 27

genome replicated and proteins translated

Question 28

what happens during the maturation stage

Answer 28

packaging of nucleic acids in capsids

Question 29

during the latent period?

Answer 29

: eclipse + maturation

Question 30

Release stage?

Answer 30

cell lysis, budding, or excretion

Question 31

which viruses are easiest to grow | and how are they grown?

Answer 31

bacterial viruses | the hosts are in liquid medium or spread as lawns on agar and inoculated with virus

Question 32

how are animal viruses and some plants grown

Answer 32

can be cultivated in tissue cultures (from animal organ in culture medium).

Question 33

number of infectious units per volume of fluid

Answer 33

titer

Question 34

Plaques are clear zones that develop on lawns of host cells where successful viral infection occurs

Answer 34

Plaque assay

Question 35

The number of plaque-forming units is always ____ | than direct counts by electron microscopy

Answer 35

lower | efficiency of infection usually much less than 100 percent

Question 36

what is required for a virus to attach to a host?

Answer 36

host specificity is a major factor | requires complementary receptors on the surface of a susceptible host for its infecting virus

Question 37

what do T4-specific proteins modify

Answer 37

proteins modify host RNA polymerase specificity to recognize only phage promoters. host transcription shut down

Question 38

Most human viral diseases are caused by?

Answer 38

RNA viruses

Question 39

what are the requirements to infect a animal cell?

Answer 39

bind specific host cell receptors, typically used for cell-cell contact or immune function Different tissues and organs express different cell surface proteins. Entry usually occurs by fusion with cytoplasmic membrane or endocytosis

Question 40

what are the two major key differences of human viral dna

Answer 40

Entire virion enters the animal cell. | Eukaryotic cells contain a nucleus, the site of replication for many animal viruses.

Question 41

where does uncoating in animal virus infection occur?

Answer 41

cytoplasmic membrane or cytoplasm.

Question 42

lysis of host cell, most common

Answer 42

acute infection

Question 43

Viral DNA exists in host genome and virions are not produced; host cell is unharmed unless/until virulence is triggered.

Answer 43

Latent infection

Question 44

Release of virions from host cell by budding does not result in cell lysis.

Answer 44

Persistent (chronic) infections

Question 45

conversion of normal cell into tumor cell

Answer 45

transformation

Question 46

: RNA viruses that replicate through a DNA intermediate (e.g., human immunodeficiency virus [HIV])

Answer 46

retroviruses