unit 2 chap 13

Question 1

How were virus discovered?

Answer 1

Ivanovsky and beijerinck
crushed up diseased plant and filtered it and applied to healthy plant but plant didn’t get sick, only got sick when given stuff not in filter

Question 2

what is the size of viruses?

Answer 2

20-900nm

Question 3

Definition of virus

Answer 3

acellular, obligate intracellular parasites

Question 4

viron

Answer 4

capsid encapsulated viruses w dna and rna molecules

Question 5

what does viral infectivity depend on?

Answer 5

depends of interaction btwn viral suface protiens and host cell surface molecules

Question 6

host range

Answer 6

range of cell types and host species is able to infect
large = rabies
small = hiv
- animal virus have tissue specifity

Question 7

basic viral infection

Answer 7

recognize host and attach
get viral genome inside host cell
make copies of viral genome
transcribe/translate viral genome to make viral proteins
assemble viral particles(virons)
exit

Question 8

viral genomes/viral genes

Answer 8

small virus; genomes encoding less than 10 genes
large virus; over 100 genes
viral gene = code for structural components, enzymes used in life cycle(replication/processing)

Question 9

genome of dna virus

Answer 9

can serve as template for transcription
can serve as template for DNA synthesis

Question 10

genome of an rna virus

Answer 10

can serve as template for translation ( +rna virus)
can serve as template for mrna synthesis ( -rna virus)
can serve as a template for DNA synthesis (retrovirus)

rna(genome)->dna->rna->protiens

Question 11

complex virus

Answer 11

have complicated structures; possess non-capsid protein components
ex. bacterophage

Question 12

taxonomy

Answer 12

a viral species is a group of viruses sharing the same genetic information and host range
- based on genome type and presence or lack of an envelope

Question 13

capsid

Answer 13

is made of capsomeres(protiens) that can vary in shape and size; helical or polyhedral

Question 14

virus envelope

Answer 14

envelope surrounds the capsid
may include glycoprotein spikes
envelope forms from host plasma membrane

Question 15

what role does glycoprotein play?

Answer 15

function in host recognition and attachment

Question 16

what are naked viruses?

Answer 16

they lack an envelope

Question 17

life cycle of animal virus?

Answer 17

attachment
- host protein, glycoprotein receptor sites
entry
- fusion(envelop virus), receptor mediated endocytosis
uncoating
- separation of genome of virus from capsid(can happen at cell membrane or nuclear membrane)

Question 18

uncoating of virus

Answer 18

2 types receptor mediated endocytosis
- uncoating w endosomes - viral receptor make an endosome surround and envelope fuse w endosome and allow genome to flow out
- uncoat at nuclear membrane - receptor of virus let it in and pass through to the nucleus, dock on nucleus and release genome in

entry by membrane fusion
- envelope virus uncoat at membrane and genome released into membrane

Question 19

lytic cycle

Answer 19

attachment
penetration(genome is the only thing that enters)
biosynthesis(production of viral DNA and viral protiens/parts)
maturation
release(lysis of host cell well by lysozyme)

Question 20

lysogenic phase

Answer 20

lytic cycle but instead assembly the phage DNA integrate into host DNA and so as it divide all the cells have phage DNA
when time mature and release like lytic

Question 21

characteristics of lysogenic cycle

Answer 21

lysogenic cells are immune to reinfection
transduction may result in phage conversion

Question 22

characteristics of animal viruses

Answer 22

• assembly of new virons(capsid and genome) occurs in the cytoplasm or nucleus
• enveloped viruses: envelope proteins are inserted into the plasma membrane or organelle membrane
• release via lysis or budding

Question 23

characteristics of dna viruses

Answer 23

• genome replication, and viral assembly in nucleus
• synthesis of viral proteins outside nucleus(w host ribosomes)
• can be template for transcription and DNA synthesis
• use host DNA polymerase

Question 24

rna animal virus

Answer 24

• genome replication, synthesis of viral protiens, and viral assembly happen outside nucleus
• rna is template for translation(in +rna virus), mRNA synthesis (in -rna)
• have rna dependant rna polymerase

Question 25

retrovirus

Answer 25

• posses reverse transcriptase and use it for DNA synthesis w genome
• goes from rna to dna

Question 26

retrovirus replication

Answer 26

• rna virus enter; has 2 same +rna and inject t helper of immune system
• uncoating release rna genome and viral enzymes(reverse transcripase) to make rna to DNA
• DNA integrate w host forming provirus and stay in persistent state
• provirus transcribe to rna to make viral proteins
• synthesized glycoprotiens insert into host membrane, viral assembly and exit w budding

Question 27

prions

Answer 27

proteins infect animals
- no nucleic acid
- ex. mad cow disease
- wrong folding of proteins
- transmitted by eat infected animal
- slow develop and resistant to physical and chemical agents

Question 28

viroids

Answer 28

not viruses
yes naked rna molecules(no capsid)
infects plants
replicated by host rna polymerase
rna no code for proteins

Question 29

latent viral infections

Answer 29

virus infect but no cause disease
stay dormant for a while
immunosuppression or stress can activate

Question 30

persistent viral infections

Answer 30

occur gradually; usually fatel
virus continuously released