DNA damage and repair

  • Created by: Sarah
  • Created on: 01-06-18 17:15
what is base excision repair used for?
to repair deaminated or depurinated bases
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what enzymes does base excision repair use to remove the damage?
(uracil) DNA glycosylase, apurinic/apyridimic endonuclease and phosphodiesterase
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what is left once dna glycosylase recognises the wrong pairing between bases and then removes that base?
phosphate backbone and sugar
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what does apyrdiminic/apurinic endonuclease do?
it removes the sugar
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what does phosphodiesterase do?
removes the phosphate
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what then happens to replace the base and everything that was removed?
leaves a primer template junction for DNA pol to extend across and add the correct base matches it with the other side and DNA ligase seals up the backbone
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what happens in deamination?
cytosine -> uracil. Uracil is mispaired with G. then in DNA rep U paired with A
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what does the CG base pair change to in deamination?
CF -> UA
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what is the most frequent DNA damage?
hydrolytic depurination + deamination of bases
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what is deamination?
removal of amino group (to carbonyl group)
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what is depurination?
removal of adenine/guanine (purines)
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what can DNA be damaged by?
oxidation, hydrolysis and uncontrolled methylation of any of 4 nucleotides
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where in DNA can be damaged?
bases, bonds within pyridimine/purines as well as bonds that link the bases to deoxyribose or within the sugar or phosphodiester backbone
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what does deamination change chemically?
removes amino acid to carbonyl group
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in depurination what nucleotides are removed?
adenine or guanine
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what is the result of depurination?
a full base pair deletion
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why is there a full bp deletion in depurination?
DNA pol reads 3 nucleotides instread of 4 because adenine/guanine has been hydrolysed out
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what is used to fix depurination/deamination?
base excision repair
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what is nucleotide exicision repair used to fix?
pyridimine dimers
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how are pyridimine dimers induced?
UV high energy radiation
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why are pyridimine dimers a problem?
the DNA pol can no longer recognise them as indvidual pyridimines as covaent reaction distorts DNA
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how does a pyridimine dimer form?
by UV causes covalent bonds to happen between carbon atoms within pyridimine rings that are adhacent to each other
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Other cards in this set

Card 2

Front

what enzymes does base excision repair use to remove the damage?

Back

(uracil) DNA glycosylase, apurinic/apyridimic endonuclease and phosphodiesterase

Card 3

Front

what is left once dna glycosylase recognises the wrong pairing between bases and then removes that base?

Back

Preview of the front of card 3

Card 4

Front

what does apyrdiminic/apurinic endonuclease do?

Back

Preview of the front of card 4

Card 5

Front

what does phosphodiesterase do?

Back

Preview of the front of card 5
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