Ch 13 Viruses Part 2

Question 1

how do animal phages differ from bacteriophages

Answer 1

the mechanisms of entering the host cell are different as well as the synthesis and assembly of new viral components

Question 2

what are the five stages of multiplication of animal viruses

Answer 2

1)attachment 2)entry 3)uncoating 4)biosynthesis 5)maturation/release

Question 3

describe attachment in animal viruses

Answer 3

receptor sites are proteins and glycoproteins
receptor sites are inherited characteristics of the host
varies from person to person (susceptibility)

Question 4

describe entry in animal viruses

Answer 4

receptor mediated endocytosis

fusion

Question 5

this is how viruses enter eukaryotic cells

molecules bound to proteins on the plasma membrane are take in by infolding of the membrane

Answer 5

receptor mediated endocytosis

Question 6

viral envelope fuses with the plasma membrane and releases the capsid into the cell’s cytoplasm
this is how enveloped viruses enter

Answer 6

fusion

Question 7

describe uncoating in animal viruses

Answer 7

separation of the viral nucleic acid from its protein coat once the virion is enclosed within the vesicle
capsid is digested when the cell attempts to digest the vesicle’s contents

Question 8

describe biosynthesis of DNA viruses

Answer 8

DNA containing viruses replicated DNA in nucleus of host by viral enzymes and synthesize capsid into cytoplasm with host enzymes
proteins then join with newly synthesized DNA to form virions (transported to ER)

Question 9

what are the four steps of biosynthesis of DNA viruses

Answer 9

1) transcription then translation
2) synthesis of capsid proteins
3) maturation occurs in nucleus
4) complete virions are released

Question 10

DNA virus

causes acute respiratory disease (common cold)

Answer 10

adenoviridae

Question 11

DNA virus
skin leisons (pus filled)
small pox/cow pox

Answer 11

poxviridae

Question 12

DNA virus
appearance of cold sores
HHV-1

Answer 12

herpeseviridae

Question 13

DNA virus
warts, tumors, cytoplasmic vacuoles
capable of transforming cells/causing cancer

Answer 13

papovaviridae

Question 14

DNA virus

cause hepatitis

Answer 14

hepadinaviridae

Question 15

describe biosynthesis of RNA viruses

Answer 15

several different mechanisms of mRNA formation occur
RNA viruses multiply in the host cell’s cytoplasm
major difference lies in how much mRNA and viral RNA are produced
(once RNA is synthesized maturation is similar)

Question 16

this is RNA within a virion that can act as mRNA

translated into two proteins which inhibit host synthesis of RNA (catalyze other strands of RNA)

Answer 16

sense strand or positive strand

Question 17

template to produce additional positive strands

Answer 17

antisense strand or negative strand

Question 18

single strand of RNA

contain RNA dependent RNA polymerase that uses negative strand as a template to produce positive strand

Answer 18

rhabdoviridae

Question 19

respiratory and digestive systems of humans

viral mRNA is produced in the cytoplasm

Answer 19

reoviridae

Question 20

enveloped viruses
single positive strand of RNA
two types of mRNA are transcribed from the negative strand

Answer 20

togaviridae

Question 21

carry reverse transcriptase

provirus

Answer 21

retroviridae

Question 22

uses viral RNA as a template to produce complementary double stranded DNA

Answer 22

reverse transcriptase

Question 23

never comes out of the chromosome

viral DNA that is integrated into the host cell’s DNA

Answer 23

provirus

Question 24

describe maturation and release in animal virus

Answer 24

assembly of protein capsid
most capsids of animal proteins are enclosed by envelope
budding

Question 25

what is the envelope protein encoded by

Answer 25

viral genes which are incorporated into the plasma membrane of the host

Question 26

process whereby the envelope develops around the capsid

Answer 26

budding

Question 27

what are the two methods of release

Answer 27

1) assembled capsid pushes through membrane | 2) nonenveloped viruses are released through ruptures in host plasma membrane

Question 28

viruses can alter properties via what

Answer 28

mutation and genetic reassortment

Question 29

virus may become more viralent | virus may become easily transmitted

Answer 29

mutation

Question 30

occurs in segmented viruses these have genomes divided into different segments (code for different info) two viruses infecting the same cell responsible for antigenic shift and antigentic drift

Answer 30

genetic reassortment

Question 31

what can plant viruses be recognized by

Answer 31

pigment loss, marks on fruit/leaves, tumors, and stunted growth

Question 32

do plants generally recover from viral infections

Answer 32

no

Question 33

are all infections bad

Answer 33

no

Question 34

what type of viruses are most plant viruses

Answer 34

RNA

Question 35

what does plant virus transmission require

Answer 35

mechanical damage to plant - viruses DO NOT attach to specific cell receptors - viruses infect plants through wound in plant cell wall

Question 36

what are virions transferred by

Answer 36

wind, animals, seeds, tubers, soil and pollen

Question 37

what are the most important agents of transmission

Answer 37

insects that feed on plants (act as vectors) | their feeding by passes cell wall protection and leaves wound that viruses can infect through

Question 38

what are many plant viruses resistant to

Answer 38

inactivation

Question 39

what does infection spread from cell to cell through

Answer 39

plasmodesmata

Question 40

describe replication in plant viruses

Answer 40

``` similar to animal viruses capsid remains outside the cell filamentous, RNA virus RNA replication and polymerase new virions assemble spontaneously ```

Question 41

group of pathogens much smaller and distinctly different from viruses

Answer 41

virions

Question 42

what do viroids consist of

Answer 42

small, circular, single stranded RNA molecule | NO protein coat (resistant to proteases)

Question 43

is a single viroid capable of infecting a cell

Answer 43

yes

Question 44

what is circular and resistant to nuclease digestion

Answer 44

viroid RNA

Question 45

do viroids act as mRNA molecules

Answer 45

no

Question 46

how do viroids replicate

Answer 46

autonomously in susceptible cells | RNA is replicated by rolling circle method using host RNA polymerase

Question 47

all identified viroids do what

Answer 47

infect plants: mechanism unknown, some latent diseases/infections

Question 48

these are proteinaceous infectious agents

Answer 48

prions

Question 49

these are linked to a number of fatal human diseases

Answer 49

prions

Question 50

what type of disease do prions cause

Answer 50

brain degeneration, brain tissue develops sponge-like holes | symptoms may bot appear for years after infection

Question 51

what is currently thought about prion proteins(PrP)

Answer 51

they are present in normal form in host animals and exposure to altered PrP causes diseases

Question 52

how did prions arise

Answer 52

following mutation to gene encoding normal PrP

Question 53

what did the mutation of PrP cause

Answer 53

protein to have different folding properties the mutated protein is resistant to proteases resists UV light and nucleases due to lack of nucleic acid

Question 54

what are prions inactivated by

Answer 54

chemicals that denature proteins