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Repair of DNA (AP endonuclease system repairs abasic sites…
Repair of DNA
AP endonuclease system repairs abasic sites
Deoxyribosephophodiesterase removes several nucleotides
DNAP replaces DNA
Apendonucleases cleave damaged DNA
DNA ligase seals bonds between new and old nucleotides
Reversal of Damage
No new DNA synthesised
Photoreactivation = photolyases use light energy to split pyrimidine dimers
Methyltransferases remove methyl groups from methylated bases
Nucleotide excision repair
Recognises kink caused in helix due to pyrimidine dimers and transcription stalling
Cleaves damage on single strand
DNAP and DNA ligase
Protein complex binds
Xeroderma pigmentosum (dry skin, hyperpigmentation and vulnerability to skin cancer) caused by mutation in this process
Cockayne syndrome (premature ageing, deafness and learning difficulties) caused by mutation in this process when repairing transcription stalling damge
Base excision repair
DNA glycolase cleaves damaged DNA but leaves a basic site
repaired by AP endonuclease system
Different DNA glycolases for different bases e.g. adenineDNAglycolase