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Test 1 FTM > Lecture 9 > Flashcards

Lecture 9 Flashcards

1
Q

What are the required components for DNA synthesis

A
  1. all four dNTPs (A,T,C,G)
  2. a fragment of DNA to act as a template
  3. DNA polymerase
  4. Mg ions
  5. a primer providing a free 3’ -OH group
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2
Q

What are the drugs Zidovudine and Didanosine?

A

They are both anti-HIV drugs that will be Incorporated into the DNA chain

However termination occurs because both of these drugs are nucleosides and do not have a 3 prime OH group

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3
Q

Explain acyclovir?

A

Is a DNA polymerase inhibitor

Lack of a 3 prime OH group

used to treat herpes simplex

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4
Q

Explain tenofovir?

A

A drug used to treat HIV

This drug competes with adenosine

This compound has no sugar, thus no OH group

this leads to termination of DNA synthesis

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5
Q

What is cytosine arabinoside?

A

This compound does have a 3 prime OH group

BUT the OH group is not positioned correctly

This leads to chain termination

adenosine arabinosid works in a similar way

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6
Q

How can the cell fix a base misincorporation?

A

DNA poly has a 3 to 5 prime proofreading exonuclease

will fix on the 3’ OH end

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7
Q

What are the players of DNA replication in prokaryotes ?

A
  1. DNaA protein (initiator protein)
  2. DNA helicase
  3. Helicase inhibitor
  4. DNA primase
  5. DNA poly I
  6. DNA poly III
  7. single stranded binding protein
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8
Q

What is the role of DNaA protein during prokaryotic DNA replication?

A

Binds to the origin of replication and breaks hydrogen bonds between the bases

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9
Q

What is the role of DNA helicase protein during prokaryotic DNA replication?

A

opens and binds primase to form primosome?

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10
Q

What is the role of the helicase inhibitor (prokaryote)?

A

delivers helicase to the DNA template

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11
Q

Role of DNA primase (prokaryote)?

A

an RNA polymerase that will synthesize a RNA primer on the lagging strand to enable DNA poly to synthesize DNA

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12
Q

role of DNA poly I (prokaryote)?

A

remove RNA primer and replace with DNA

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13
Q

role of DNA poly III (prokaryote)?

A

synthesis of leading and lagging strands

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14
Q

Role of ssb?

A

binds to single stranded DNA in the replication bubble and prevents it from re-annealing

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15
Q

Model of initiation of replication at E.coli OriC?

A
  1. DNaA proteins will bind to the 9-mers at the origin
  2. strand separation occurs at the region of the 13-mers
  3. Helicase inhibitor protein delivers helicase
  4. helicase clamps around each strand of DNA
  5. Helicase will unwind the DNA
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16
Q

How to prevent single stranded DNA from reanneling (prokaryotes)?

A

SSB proteins

17
Q

How are the okazaki fragments joined together in prokaryotes?

A

DNA ligase

18
Q

How is the DNA poly III loaded and maintained on the single stranded DNA template?

A

Clamp proteins.

these proteins hold DNA poly onto the template for synthesis

19
Q

How can positive supercoiling be reversed?

A

topoisomerase enzymes

20
Q

What is the role of DNA gyrase (prokaryotes)?

A

This enzyme introduces negative supercoils into the DNA…. this reduces positive supercoiling by opening the DNA

21
Q

What is ciprofloxacin?

A

this is a drug that inhibits bacterial DNA gyrase

used to treat respiratory and urinary tract infections

22
Q

What are the eukaryotic DNA polymerases?

A

Polymerase alpha

polyermase theta

23
Q

What is the role of polymerase alpha (eukaryotes)?

A

synthesizes RNA primer on the leading and lagging strand

subunit possesses primase activity and initiates DNA synthesis

low processivity- falls off after short segment

no exonuclease activity

24
Q

What is the role of polymerase theta (eukaryotes)?

A

Synthesis DNA from leading and lagging strands

main replicative enzyme

high processivity- can synthesize long stretches of DNA

3 to 5 exonuclease activity

25
Q

Explain camptothecin?

A

this is an anti cancer drug that binds to and inhibits the activity of topoisomerase I in eukaryotes

this leads to DNA breakage

26
Q

Explain eptoside?

A

anti cancer drug that inhibits the activity of topoisomerase II

27
Q

What does actinomycin D (dactinomycin) do?

A

prevents DNA replication

prevents the formation of regions of ss DNA
inhibits RNA transcription

28
Q

Differences between prokaryote and eukaryote DNA replication

A

Prokaryote- only one origin of replication
DNA poly I and III
primers are removed different (DNA poly I)

eukaryote- multiple origin of replication
Polymerase alpha and theta

Test 1 FTM (35 decks)

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