dna repair 2 Flashcards
what are the two types of repair
sequence repair and molecule repair
what is direct sequence repair?
where the damage had converted the nt into something else, and where during repair you are able to convert it back into the original base
what do we use to undo alkylation and how does it work
specific reversal proteins
- this transfers the methyl group back onto itself
how do we break dimers formed between thymine and what enzyme do we use
we use photolysis and dna photolyase
it absorbs blue light and breaks the dimer and this uses 2FADH
what is base excision repair and which enzymes carry this out
removal of individual bases
dna glycolyases
how do dna glycosylases work
they recognise abnormal bases and cleave them and this leaves an absic site
how do dna glycosylases work
they recognise abnormal bases by flipping the base out and cleaving them and this leaves an abasic site
what will pol b do in dna repair
replace an abasic nt
what is nucleotide excision repair and what triggers it
removal of oligonucleotide fragments from one strand
triggered by structural change
what can ner repair
any kind of sequence damage
what protein complex carries out ner in bacteria
UvrABC exonuclease
how is ner carried out
uvrc and b will move along the DNA and cleave the fragment of dna
what is mismatch repair
the detection and removal of incorrect base pairs
how are mismatched pairs detected
a mismatched pair will distort the helix and will be detected by specialist proteins
which base will be corrected in the mismatch repair
the daughter strand
which protein will identify the daughter strand and cleave it
mutH
which proteins will bind to the distortion
mutL/mutS complex
what is the multi prong approach and what are the enzymes
the use of 3 different enzymes to prevent 8-oxo-G
mutT, mutM, mutY
what is translesion synthesis
specialised polymerases that are able to continue duplicating despite there being damage on the DNA, will not stall
how does homologous recombination work
while sister chromatids are still joined, the other can be used as a template for the other
how does non-homologous end-joining work
a protein complex binds at the naked end of the strand and makes DNA ligase 6 join the 2 pieces together, but it will bind any old DNA together
what does a defect in the ner mechanism form
xeroderma pigmentosum
what does a defect in the mismatch repair mechanism cause
hereditary non-polyposis colon cancer
