Excision repair Flashcards
Name the 2 types of excision repair
Base and nucleotide
name the 3 enzymes in Excision repair
Repair endonuclease, polymerase and ligase
DNA Repair endonuclease is what
complex that recognises and binds to and excised the damaged base or bases
DNA polymerase does what
fills the gap, using the undamaged complementary strand of DNA as a template
DNA Ligase does what
seals the break left by DNA polymerase
Base excision repair does what
pathways remove abnormal chemically modified bases
Nucleotide excision repair does what
pathways remove larger defects, such as thymine dimers
Base excision repair is initiated by what enzyme
DNA Glycosylases
Explain what happens first in base repair
-Glycosylase binds to the modified base and cleaves the glycosidic bond between the abnormal base and pair.
What is an AP site
A site on the DNA that is missing a base
What happens at the AP site involving the AP endonuclease (Base)
The sugar phosphate backbone is removed by the AP endonuclease and phosphodiesterase
What remains after AP endonuclease and phosphodiesterase has been used (Base)
Missing nucelotide
DNA polymerase then does what and leaves what (Base)
replaces the missing nucleotide but a single strand break still remains
What seals the single strand break (Base)
DNA ligase seals the nick
Nucleotide Excision repair - ‘excinuclease’ activity requires the products of what genes
uvrA
uvrB
uvrC
What polypeptide trimer recognises and binds to the damaged DNA in nucleotide repair
Trimer of 2 uvrA and one uvrB
uvrA is a dimer
Energy from what is used to bend the DNA at the damaged site and what is released
ATP
uvrA dimer is released
uvrC binds to what
the uvrB/DNA complex
uvrB and uvrC cleave what on the damaged DNA
uvrB cleaves the 5th phosphodiester bond from the 3’ side.
uvrC cleaves the 8th phosphodiester bond from the 5’ side
uvrD is also known as what
DNA helicase II
uvrD/Helicase II releases what
the excised ogliomer
DNA polymerase and ligase then do what in nucleotide repair
replaces and seals
