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Excision repair - Coggle Diagram

- - - - not looked at yet
    - - damage e.g. uracil incorporation
        
        DNA glycosylase cleaves N glycosyl bond (between base and backbone)....... leaves abasic site
        
        AP endonuclease cleaves backbone at 5' end of Abasic site, leaves a flap of backbone
        
        DNA polymerase fills in the abasic site based on exposed nucleotide on other strand, replaces some backbone under the flap
        
        dRP lyase cuts the flap at the 3', leaving a nick between replacement backbone and original
        
        DNA ligase seals the nick
        
        DNA glycosylase is the only enzyme binding to a specific base or damage
        
        and so there are several different glycosylases in comparison to the other enzymes
        
        How does the enzyme check the base if it is under the backbone
        
        N-glycosyl bond is a single bond, therefore is able to rotate about the carbon
        
        so the enzyme flips the base out quickly to check it
      - What is it used for
        
        mainly intrinsic factors that have existed for a long time, as they are conserved evolved things
    - - protein complex of 2x UvrA and 2x UvrB
        
        UvrA detects DNA damage by detecting changes to DNA flexibility
        
        UvrB is loaded onto each strand at lesion
        
        UvrA dissociates and UvrC binds UvrB
        
        UvrC has 2 nuclease domains and cuts either side of the lesion on DNA (3' then 5')
        
        UvrD (DNA helicase) overcomes the hydrogen bonds between bases
        
        1 more item...
- - - - ionising radiation
      - DNA damaging agent
      - replication past a nick (good image in onenote)
      - inappropriate nuclease activity
    - - meiotic recombination
      - V(D)J recombination
  - - - heterodimer ring of Ku70/80 form around each exposed end (assist in recruitment of other proteins)
        
        DNA-PK (kinase) and artemis (nuclease) are recruited... artemis chews back one strand on each exposed end
        
        hopefully short regions of microhomology form (small sticky ends (1-4 nt))
        
        strands are annealed by DNA ligase
      - look at V(D)J recombination.... very similar process
    - - process usually introduces mutations from the original sequence, could be harmful