Lecture 40 - Viral Biosynthesis

Question 1

what is the goal of biosynthesis

Answer 1

generate components to assemble viral progeny

Question 2

in a DNA genome, whose enzymes are used

Answer 2

cell - DNA to mRNA
cell or viral - DNA to DNA

Question 3

in a RNA genome, whose enzymes are used

Answer 3

viral - RNA to RNA

Question 4

in a retrovirus, whose enzymes are used

Answer 4

viral - RNA to DNA (reverse transcriptase)
viral - integration (DNA to viral DNA)
cell - viral DNA to RNA

Question 5

what copies RNA genome into a DNA copy in a retrovirus

Answer 5

reverse transcriptase

Question 6

what cuts cell DNA and inserts viral DNA in retroviruses

Answer 6

integrase

Question 7

T/F: integrase determines mutation rate

Answer 7

FALSE - polymerase type

Question 8

T/F: RNA polymerases have a higher error rate because they lack exonuclease

Answer 8

TRUE

Question 9

what is the function of exonuclease

Answer 9

proof-reading

Question 10

why is it difficult to “cure” HIV?

Answer 10

integrated to cell genome

Question 11

what are the 3 steps of biosynthesis

Answer 11

1. generate mRNA
2. translate mRNA to generate protein
3. replicate viral nucleic acid

Question 12

viruses with a ____ genome can use ____ enzyme

Answer 12

DNA; cell

Question 13

what kind of drug should be used for viruses with DNA genome

Answer 13

an antiviral agent that incorporates into viral DNA so cell RNA polymerase cannot “read” it

Question 14

T/F: antiviral drugs that inhibit RNA polymerase that “read” RNA genomes will not block normal cell processes

Answer 14

TRUE

Question 15

summarize the 3 steps viral mRNA is made into protein

Answer 15

1. large mRNA translated to polyprotein
2. polyprotein cleaved to functional proteins by viral protease
3. generation of multiple mRNA and translation to individual proteins

Question 16

antiviral agents, like current HIV drugs, inhibit what

Answer 16

viral protease

Question 17

what are 2 antiviral agents for DNA polymerases

Answer 17

1. nucleoside/nucleotide analog
2. non-nucleoside revese transcriptase inhibitor

Question 18

nucleoside analogs inhibit what

Answer 18

polymerase function

Question 19

what 2 ways do nucleoside analogs inhibit polymerase function

Answer 19

1. chain terminators
2. polymerase inactivators

Question 20

T/F: a nucleoside analog must undergo 3 phosphorylations to become active

Answer 20

TRUE

Question 21

summarize chain terminators

Answer 21

• DNA polymerase inserts nucleoside in growing DNA chain and can’t accept any more nucleotides
• high affinity for viral polymerase
• low affinity for cell polymerase

Question 22

summarize polymerase inactivators

Answer 22

• delivered as inactive drug
• bind viral polymerase better than cell polymerase
• active only in infected cells

Question 23

what antiviral agents are used for retroviruses

Answer 23

1. those that inhibit viral polymerase
2. inhibit viral integrase