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Biochem > DNA Replication and Repair > Flashcards

DNA Replication and Repair Flashcards

1
Q

Significant features of Origins of Replication?

A

Rich in A-T base pairing, makes it easier to unwind

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2
Q

What prevents 2 unwound DNA strands from annealing back together thru complementary base pairing?

A

Single-strand DNA binding proteins

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3
Q

Secondary function of SSDBPs?

A

Protect ssDNA from DNase nuclease activity

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4
Q

Function of Ciprofloxacin?

A
  • wide spectrum bacterial antibiotic topoisomerase inhibitor
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5
Q

Function of Irinotecan and Topotecan?

A
  • Type I topoisomerase inhibitors
  • used to tx colorectal and ovarian cancer
  • inhibit ligation step
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6
Q

Function of Doxorubicin (adriamycin), etoposide, and ellipticine?

A
  • Type II topoisomerase inhibitors

- tx many types of cancer

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7
Q

What is a processive polymerase? Example?

A
  • can cont long stretches of DNA synth w/o falling off

- DNA Pol III

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8
Q

DNA Pol I function

A
  • synth of short stretches of DNA on lagging strand

- fills in mature Okazaki fragments & removes primers

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9
Q

Function of DNA Pol alpha

A
  • synth RNA primers w/ RNTs
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10
Q

Function of DNA Pol delta

A
  • lagging strand synth
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11
Q

Function of DNA Pol epsilon

A
  • leading strand synth
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12
Q

Function of DNA Pol beta

A
  • repairs damaged DNA
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13
Q

What proteins remove RNA primers in eukaryotes?

A
  • complex containing FEN-1 and RNAse H
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14
Q

Why are telomerase inhibitors used in cancer tx?

A
  • cancer cell lines become immortal by activation of telomerase activity
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15
Q

Function of AZT in HIV tx

A
  • thymidine analog that replaces 3’-OH group w/ 3’-azide group
  • terminates strand for HIV RT
  • prevents viral replication
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16
Q

Function of DDI in HIV tx

A
  • purine analog
  • hydrogen @ 2’- and 3’-carbons
  • causes chain termination
17
Q

What viruses does Acyclovir treat? (3)

A
  • herpes simplex
  • varicella zoster (chickenpox)
  • herpes zoster (shingles)
18
Q

What is Gancyclovir used to treat?

A
  • cytomegalovirus (CMV) retinitis (blindness)
19
Q

Mechanism of Gancyclovir and Acyclovir? (4)

A
  • guanosine analogs
  • guanosine phosphorylated in infected cells by viral kinase
  • drugs incorporated into viral genome
  • prevent replication
20
Q

What does cytosine form after deamination?

A

Uracil

21
Q

When is Base Excision Repair (BER) used?

A
  • when damage results in change in a base on 1 strand of DNA duplex
22
Q

Deamination of 5-methylcytosine leads to ?

A

Thymine

23
Q

When is Nucleotide Excision Repair (NER) used?

A
  • when damage –> larger lesions in DNA (eg thymidine dimers from UV)
24
Q

NER mechanism? (4)

A
  • XP-C or Rad23B recognize bulge in DNA
  • recruitment of DNA helicase activity (TFIIH)
  • XP-F and XP-G endonucleases remove path around lesion
  • DNA pol repairs region
25
Q

Function of Cisplatin? (3)

A
  • anti-cancer drug
  • causes DNA adduction
  • DNA damage should kill cancerous cells thru apoptosis
26
Q

Clinical implication of XP-F (ERCC1)?

A
  • confers resistance to Cisplatin
27
Q

When is Mismatch Excision Repair (MER) used?

A
  • corrects errors not caught during replication that cause mismatched BPs
28
Q

Cause of hereditary nonpolyposis colorectal cancer?

A
  • mutation in a copy of MLH1 or MSH2 (supposed to detect mispairing)
29
Q

Cause and effect of Xeroderma pigmentosum?

A
  • cause: defect in an NER gene –> inability to globally repair UV damaged DNA
  • effect: predisposed to cancer
30
Q

Cause and effect of Cockayne syndrome?

A
  • cause: defect in transc-coupled repair

- effect: neuro defects and premature aging

31
Q

What 2 genes are mutated in Cockayne syndrome?

A
  1. ERCC8 (interacts w/ TFIIH)

2. ERCC6 (helicase)

32
Q

Most common use of BER?

A

Fixing 5MeC to T mutation

33
Q

Most common use of NER?

A

Fixing thymidine dimer mutation

Biochem (9 decks)

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