DNA repair Flashcards
What does photolyase do? What does it require to function? What organisms have it?
Breaks photodimers. It requires light to function and is found in bacteria, plants, fungi, and some animals
What does alkyltransferase do?
Removes alkyl groups and repairs damage from alkylating agents
What is the base excision repair pathway? What does it target?
It cuts a single base that doesn’t distort the double helix
What enzymes are used in the base excision repair pathway?
DNA N-glycosylases
What are the 4 steps in the base excision repair pathway?
- DNA glycosylase removes the damaged base by cutting the bond between it and the sugar
- AP endonuclease makes a cut 5’ to the removed base
- DNA is removed and replaced
- DNA ligase seals the break
What is the nucleotide excision repair pathway? What does it repair?
Removes a section of DNA around a damaged area. Targets photodimers, areas with lots of damaged bases, bulky DNA damage that blocks transcription
What enzymes are required for the nucleotide excision repair pathway? What signals them to come fix a problem?
Uvr proteins. Has transcription coupled repair, RNA polymerase signals Uvr proteins to come if it gets stick
What are the 5 steps in the nucleotide excision repair pathway?
- Transcription is blocked and the damage is recognized
- Multi protein complex is assembled
- Area around the damaged nucleotides is cut by Uvr C and removed by Uvr D
- DNA polymerase fills in the gap
- Sealed by DNA ligase
What are the proteins involved in mismatch repair? What are their functions?
MutS, MutH, and MutU
MutS recognizes a mismatched pair and recruits MutH. They cut out an area around the mismatch and MutU removes it and DNA polymerase fills in the gap
What would cause DNA to not be repaired?
There’s too much damage for the enzymes to keep up with
