lecture 3 content

Question 1

why do effective viruses not kill hosts

Answer 1

b/c without a living host the viruses is unable to effectively transmit

Question 2

what are the steps in virus replication

Answer 2

1. attachment( virus interacts w the cell surface through viral surface protein interations w cell glycoproteins)
2. entry (in enveloped viruses fusion takes place woth teh surface membrane and in non-enveloped the virus is internalized by the cell vis lysis or permeabilization)
3. repllication of genome and protein production (after infection the particles enter the eclipse phase where no particles can be ioslated form infected cell followed by log phase where virus particels ebing to be released then finally cell death)
4. virus regulation of cellular activites (modifying the cell cycle, affecting protein translation which is often to allow for hijacking of the machinery)
   5.assembly
   6.release

Question 3

why are pigs considered the mixing vessel for viruses

Answer 3

bc they share some of the same sialic acids on the cell surface as that of humans

Question 4

types of entry into a vesical

Answer 4

clathrin mediated (in vagination)
calveolae mediated (lipid raft)
macropinocytosis(phagocytosis)

Question 5

what strategies do viral partials have that allow for them to enter the nucleus of the cell

Answer 5

1. nuclear localization signals which allow for passage
2. small enough to float threw nuclear pore
3. disassemble to fit in nuclear pore
4. enter the nucleus during cell division

Question 6

segmented genomes

Answer 6

cause for huge genetic variation as genes are exchange with other viruses along with random mutations

Question 7

antigenic drift vs shift

Answer 7

drift is when mutational chnages arise during replication

shift is when genes from another genome are exchanged

Question 8

what are the 4 hypothese related to why HIV mutates so rapidly

Answer 8

1. reverse transcriptase is a low fidelity polymerase(lots of errors)
2. reverse transcrptase jumps form one genome to the other
3. many HIV particles are infected in the same cell causes re asstotment
4. recombination during DNA intergration

Question 9

how to DNA viruses obatin machinery to replicate DNA

Answer 9

1. wait for cell to divide
2. induce the cell to enter S phase
3. Make their own enzymes

Question 10

how to over come the end replication problem

Answer 10

Circularization or bidirectional transcription

Question 11

what are the problesm assoiated with RNA genomes

Answer 11

RNA is less stable then DNA

CEll does not have a RNA dependent RNA polymerase thus the virus must bring its own

RNA polyermaseses have very low fidelity

Question 12

Brief discrpition of positive sense ssRNA genomes

Answer 12

Since they are directly realted to RNA they can be translated directly(ifectious genome)

can be used to make negative sense RNA which is then used to make more RNA

Question 13

briefly describe negative sense RNA genomes

Answer 13

they are not infectious and connot be directly translated to proteins therefore must bring its own RNA poly

Question 14

how to control protein levels

Answer 14

events at gene junctions which limit amm of protein being produced such as capping failre to terminate trasncription and polyadcenylation

Question 15

retrovirus

Answer 15

Diploid
cotain GAG POL and ENV genes
transcriptase jumps bewteen strands thus causing gene veriation

Question 16

what are the Oncogenic effects of HIV

Answer 16

Intergration of genome affects adjacent cell cycel wontriolling genes disrupting or enhancing their function

expression of viral oncogenes

Question 17

what are the 2 options for virus release

Answer 17

Cell lysis or budding

Question 18

what are the 3 kinds of cell lysis

Answer 18

Viroproin– encode proteins late in infection that disrucp the cell mmebrane

Lytic phospholipids– virues may indice the synthesis of lytic phospholipds

Lysozymes– encode of lysozymes that digest the cell wall