Viruses

Question 1

main components of viral structure

Answer 1

nucleic acids (DNA or RNA) 
Capsid (houses DNA, has capsomere)

potentially have envelope

Question 2

envelope

Answer 2

additional structure of viruses

can have spikes

Question 3

spike important for attachment

Answer 3

HA

Question 4

how is the envelope generated?

Answer 4

composed of host cell membrane (acquired during maturation or release)

mostly plasma membrane but can be Golgi

Question 5

stages of viral life cycle

Answer 5

1. attachment
2. entry
3. uncaring
4. Biosynthesis (replicating genome, transcription/translation of proteins)
5. Assembly, maturation, and release

Question 6

which phase of viral life cycle allows you to distinguish viruses?

Answer 6

biosynthesis

can distinguish between retroviruses, double/single strand, DNA/RNA viruses

Question 7

after double stranded DNA viruses are uncoated….

Answer 7

their genome goes to the nucleus (unique to DNA)

Question 8

what is required for replication of double stranded DNA viruses?

Answer 8

must make more DNA

so you use DNA for transcription for transcription and translation for replication by viral RNA dependent RNA polymerase

Question 9

for RNA viruses, does creation of DNA/RNA viruses occur?

Answer 9

no. this is unique to DNA viruses (no DNA in replication cycle)

Question 10

what is unique about retroviruses?

Answer 10

reverse transcriptase, uses spikes to attach host cell

it takes RNA to create DNA

Question 11

multiplication of retrovirus

Answer 11

nucleus contains 2 identical + strands of RNA

enters by fusion via spikes

uncaring releases reverse transcriptase, integrate, protease

reverse transcriptase copies vRNA to make double strand DNA

Question 12

how to viruses cause cancer

Answer 12

bring their own oncogenes and insert into host genome

cause conversion of host cells proto-oncogenes

suppress or interfere with host tumor suppressor genes (alter cell regulation)

bind to tumors suppressor genes themselves

insert promotor/enhancer next to oncogene in cell

Question 13

what is lysogeny?

Answer 13

when phage integrates into host cell DNA and exists as a prophage – stays until appropriate conditions occur (lytic)

allows it to be transferred to progeny

allows it to be transferred

Question 14

lysogenic life cycle

Answer 14

phage DNA integrates into host DNA, gets copied when cell divides

triggers (i.e. UV light) triggers excision from host

Question 15

lytic life cycle

Answer 15

activated via lysogenic cycle

directs synthesis of new phages until the cell lyses and releases new viruses into body

Question 16

what type of horizontal gene transfer is seen by lysogenic cells?

Answer 16

transduction

Question 17

type of bacteriophages undergo lysogeny?

Answer 17

temperate phages

give rise to specialized transduction

Question 18

protein infectious particles are found in:

Answer 18

yeast, brain, sheep, cows

cause disease in their respective host, and can cause human disease

Question 19

Prion in cows

Answer 19

BSE/mad cow disease

Question 20

prion in sheep

Answer 20

scrapie

Question 21

prion in humans

Answer 21

kuru

Question 22

viruses differ from bacteria in that viruses:

a. don’t have nuclei
b. obligate intercellular parasites
c. filterable
d. not composed of cells

Answer 22

d. not composed of cells

Question 23

what distinguishes chronic viral infection from latent viral infection?

a. remains in equilibrium
b. it can be reactivated by immunosuppression
c. viruses appear suddenly
d. infectious virus gradually builds up over long periods of time

Answer 23

d. infectious virus gradually builds up over long periods of time

reactivated = latent
suddenly= acute