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MCP Unit 1 > Lecture 6: DNA Repair And Replication > Flashcards

Lecture 6: DNA Repair And Replication Flashcards

0
Q

What type of genome instability characterizes Down syndrome, klinefelter’s syndrome, patau syndrome, and triple-X syndrome?

A 
Whole xs loss or gain
Down trisomy 21
Klinefelter's XXY
Patau trisomy 13
Triple X XXX
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1
Q

What type of genomic instability characterizes fragile X syndrome and Huntington’s disease?

A

Large scale repeat expansion

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2
Q

In what direction are phosphodiester bonds formed in replication?

A

5’ –> 3’

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3
Q

Describe conservative and dispersive models of DNA replication

A

Conservative: daughter DNA has two new strands
Dispersive: bits and pieces

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4
Q

What did the Meselson-Stahl experiment show?

A

DNA replication is semi-conservative

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5
Q

What are the four phases of interphase?

A

M G1 S and G2

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6
Q

What enzyme performs proofreading for DNA-pol, and in what direction does it work?

A

Exonuclease 3’ –> 5’

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7
Q

How do exonuclease and endonuclease differ?

A

Exo: chews from end, only proceeds in one direction (3 to 5), involved in DNA rep
Endo: cuts like scissors within DNA, not involved in DNA rep

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8
Q

Does DNA-pol have proofreading ability?

A

Yes - exonuclease

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9
Q

Which DNA repair mechanism corrects 99% of replication errors?

A

DNA mismatch repair

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10
Q

Which genes are mutated in Hereditary Non-Polyposis Colon Caner?

A

Mismatch repair genes

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11
Q

What is the phenotype called in hereditary non-Polyposis colon cancer? Which genes are mutated?

A

Mutator phenotype

Mismatch repair genes

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12
Q

Which DNA-pol family replicates chromosomes?

A

B

Pol alpha, gamma, epsilon

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13
Q

What type of replication and repair does DNA-Pol A family do?
(Pol-gamma)

A

Mitochondrial

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14
Q

In which process are DNA-PKcs, Ku, DNA ligase IV-XRCC4, Artemis, XLF, and Metnase involved?

A

Double stranded break repair

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15
Q

Defects in ATM causes which syndrome?

A

Ataxia telangiectasia

16
Q

Mutation of BLM protein causes which syndrome?

A

Bloom Syndrome

17
Q

What do the terms ataxia and telangiectasia mean?

A 
Ataxia = abnormal balance
Telangiectasia = dilation of blood vessels
18
Q

Which syndrome has sensitivity to gamma irradiation, susceptibility to lymphomas, dilation of blood vessels in skin and eyes, and immune dysfunction?

A

Ataxia telangiectasia

19
Q

Which syndrome has sensitivity to mild alkylating agents, susceptibility to carcinomas, leukemias, and lymphomas, and facial telangiectases?

A

Bloom syndrome

20
Q

What is the function of BLM? What syndrome is caused by its mutation?

A

RecQ helicase. Replication stress response. Bloom syndrome

21
Q

What is the function of ATM? What syndrome does its mutation cause?

A

Protein kinase in replication stress response. Upregulates p53. Ataxia telangiectasia

22
Q

What do AZT, ddC, and ddI have in common?

A

Nucleotide analogue chain terminators
AZT - HIV
ddC and ddI - cancer

23
Q

What do hydroxyurea, camptothecin, and 5-FU have in common? What do they target?

A

Enzyme inhibitors
Hydroxyurea- RNR (depletes deoxyribonucleotides)
Camptothecin- Top1
5-FU - thymidylate synthetase (depletes dTTP)

24
Q

Are alkylation and deamination of DNA regulatory or detrimental?

A

Detrimental

25
Q

How are pyrimidine dimers and alkylation of DNA repaired?

A

Direct reversal by enzymes
These are template-independent damage
Photoreactivation by photolyase for pyrimidine dimers
O-methylguanine methyltransferase for alkylation

26
Q

What are three repair mechanisms for single strand DNA damage?

A

Base excision repair (BER)
Nucleotide excision repair (NER)
Mismatch repair (MMR)

27
Q

Comparing base excision repair and nucleotide exchange repair, which is more bulky?

A

NER is bulky

28
Q

BER, NER, and MMR differ in the enzymes used in first step of repair. How is this first step characterized?

A

DNA repair nucleases hydrolyze phosphodiester bonds. Leaves small gap in helix

29
Q

BER, NER, and MMR share steps 2 and 3 of repair. Which two enzymes act in these steps?

A

DNA-pol

DNA ligase

30
Q

What is a downfall of NHEJ?

A

Minor changes in sequence

Can join previously unlinked DNA molecules

31
Q

Defects in NER, and also in XPV - although the two are not related - can result in what syndrome?

A

Xeroderma pigmentosum

32
Q

Severe predisposition to skin cancers is associated with which recessive hereditary syndrome?

A

Xeroderma pigmentosa

33
Q

Like XP, this other disease is associated with defects in NER

A

Cockayne syndrome

34
Q

What are the first proteins to act in dna replication?

A

Initiator proteins

MCP Unit 1 (7 decks)

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