Week 6 - Repair Flashcards
1
Q
completing the repair
A
- Mut complex binds mismatch and puts a nick when GATC is encountered
- GATC is encountered in 2 ways
2
Q
upstream GATC
A
- 5’ exonuclease will hydrolyze large fragment
- DNA pol fills fragment and leaves nick
- DNA helicase seals nick
3
Q
downstream GATC
A
- 3’ exonuclease will hydrolyze large fragment
- DNA pol (3’ proofreading activity) fills fragment and leaves nick
- DNA helicase seals nick
4
Q
proteins required in mismatch repair
A
- MutL/MutS
- MutH
- helicase/exonuclease
- pol
- ligase
5
Q
eukaryotic flagging
A
there’s a different flagging process for eukaryotes as eukaryotes do not have hemimethylated strands
6
Q
base excision
A
- repairs spontaneous deamination mutations
- identifies abnormal bases
7
Q
base excision repair mechanism
A
- DNA glycosylase identifies abnormal base
- AP endonucleas binds to AP site and breaks phosphodiester bond
- DNA pol 1 removes overhang phosphorus
- nick is sealed by DNA ligase
8
Q
DNA glycosylase
A
recognizes abnormal base then breaks the N-beta-glycosyl bond
9
Q
proteins required in base excision repair
A
- DNA glycosylases
- AP endonucleases
- 5’ exonuclease
- DNA pol 1
- DNA ligase
10
Q
nucleotide excision repair
A
- fixes distortions of the helix
- the only repair humans need (pyrimidine, usually thymine, dimers)
- important in skin
11
Q
nucleotide excision repair mechanism
A
- excinuclease binds pyrimidine dimer
- helicase unwinds ds region
- excinuclease creates 2 nicks
- DNA pol 1 and DNA ligase stabilize ss DNA, create new strand, and seals nicks
12
Q
xeroderma pigmentosum
A
mutation in any gene that’s invovled in repair of thymine dimers
