Week 5 - Repair Flashcards
mutation causes
- spontaneous chemical changes
- oxidative change
- radiation
- chemicals
spontaneous deamination
- cytosine becomes uracil
- adenine becomes hypoxanthine
- higher rates
hypoxanthine
binds with cytosine well (A=C)
spontaneous depyrimidation
- cytosine to uracil
- 5-methylcytosine to thymine
- adenine to hypoxanthine
- guanine to xanthine
- lower rates
oxidative change
oxphosphorylation generates free radicals that can damage DNA
oxphosphorylation/aerobic catabolism
donates electrons to oxygen
free radicals
- hydrogen peroxide
- superoxide
- hydroxyl radicals
radiation
creates rigid cyclobutyl ring between two bases which will not fit active site ot DNA polymerase
repair mechanisms in E. coli
- mismatch repair
- base excision repair
- nucleotide excision repair
mismatch repair
repairing an accident of replication that was not proofread
base excision repair
repairing abnormal bases (bases from deamination/depyrimidation)
nucleotide excision repair
repairing of structural distortion (thymine dimers from UV)
methyl-directed mismatch repair mechanism
- strand discrimination
- strand marking
- repair
strand discrimination
old strand is identified before Dam methylase methylates new strand
strand marking
- MutS binds to the mismatched complex
- forms a complex with MutL
- complex hydrolyzed through ATP flags mismatch
