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Cancer Cell Biology > 3 - DNA Damage and Repair > Flashcards

3 - DNA Damage and Repair Flashcards

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1
Q

What are mobile genetic elements?

A

viruses

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2
Q

What is endonuclease?

A

cuts between phosphodiester bond | cuts DNA

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3
Q

What is glycosylase?

A

pulls out the bases = separates base from DNA strand

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4
Q

What are the 2 DNA repair pathways for excision repairs?

A

BER (bases) | NER (nucleotides)

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5
Q

What is the function of methylation?

A

deactivates gene | happens on specific sites of DNA

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6
Q

What is CpG?

A

areas in the DNA where Cs and Gs are next to each other

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7
Q

Where in the DNA would methylation ONLY occur?

A

on a C that is next to a G (CpG)

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8
Q

How likely is demethylation?

A

rare

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9
Q

Where are CpG islands located?

A

promoter regions of housekeeping and tissue specific genes

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10
Q

What does CpG-island methylation lead to?

A

inhibits transcription factors from accessing it bc a bunch of proteins jump onto methylated site = silences gene

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11
Q

How can CpG methylation lead to cancer?

A

if the wrong genes are silenced/turned off

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12
Q

How can CpG methylation be used as a cancer therapy?

A

can silence the proto-oncogenes or mutated genes that cause the cell to run wild

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13
Q

What is Base Excision Repair (BER)?

A

removes the damaged base | more active | transcription-coupled repair pathway

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14
Q

What is Nucleotide Excision Repair (NER)?

A

removes a stretch of nucleotides | more specific | can be coupled with transcription

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15
Q

What are the enzymes used in BER?

A

glycosylase, endonuclease, exonuclease, DNA pol beta, ligase

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16
Q

What is the function of glycosylase in the “flipping out” mechanism?

A

flips one of the bases out and clips it = abasic site

17
Q

What is the function of endonuclease in the “flipping out” mechanism?

A

clips on 5’ or 3’ BUT nicks DNA in ine space

18
Q

Which polymerase fills out the clipped spot from endonuclease in the “flipping out” mechanism?

A

DNA polymerase beta

19
Q

What is the function of ligase in the “flipping out” mechanism?

A

fixes by reforming the phosphodiester bonds

20
Q

What are scaffolding genes?

A

proteins that bring in other proteins involved in the DNA repair

21
Q

What kind of gene are the BRCA1 (breast cancer) genes?

A

scaffolding genes

22
Q

What does a mutation in the BRCA1 gene indicate?

A

something going on in the DNA repair mechanisms

23
Q

What does NER fix?

A

thymine dimers | big adducts causing bulky lesions blocking DNA replication

24
Q

What are the enzymes used in NER?

A

endonuclease, DNA polymerase, ligase

25
Q

What is the process for NER?

A

nick, nick between lesion (endonuclease) &raquo_space;> lift lesion strand out &raquo_space;> fill (DNA polymerase and ligase)

26
Q

What results from a mutation in a protein involved in the NER pathway?

A

xeroderma pigmentosum

27
Q

What is xeroderma pigmentosum?

A

person sensitive/allergic to UV light = can only come out at night = skin cells cannot repair thymine dimers

28
Q

What is the difference between xeroderma pigmentosum variant and classical?

A

biochemical: classical = defect in early step of NER | variant = defect in translesion bypass

29
Q

What is Trichothiodystrophy?

A

scaly skin due to dying skin cells from a mutation in one of the parts of the NER mechanism

30
Q

What are the 5 recombinational DNA repair mechanisms?

A

daughter strand gap repair | homologous recombination (HR) | non-homologous end-joining (NHEJ) | break-induced repair (BIR) | interstrand-crosslinks

31
Q

What brings in the BRCA proteins?

A

checkpoint proteins

32
Q

What does sporadic mean?

A

accumulation of mutation throughout our lifetime

33
Q

What would NHEJ repair mechanism be used for?

A

if chromosome cannot find its partner | not preferable because results in many mismatches

34
Q

In NHEJ repair mechanism, how is it trying to fix a mutation?

A

cell is looking for 2 areas that are closely complimentary = give it enough H-bonds to stick

35
Q

Why are lesion-replication polymerases error prone to normal DNA?

A

they have loose specificity

Cancer Cell Biology (17 decks)

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