dna repair 2

Question 1

what are the two types of repair

Answer 1

sequence repair and molecule repair

Question 2

what is direct sequence repair?

Answer 2

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

Question 3

what do we use to undo alkylation and how does it work

Answer 3

specific reversal proteins
- this transfers the methyl group back onto itself

Question 4

how do we break dimers formed between thymine and what enzyme do we use

Answer 4

we use photolysis and dna photolyase
it absorbs blue light and breaks the dimer and this uses 2FADH

Question 5

what is base excision repair and which enzymes carry this out

Answer 5

removal of individual bases
dna glycolyases

Question 6

how do dna glycosylases work

Answer 6

they recognise abnormal bases and cleave them and this leaves an absic site

Question 6

how do dna glycosylases work

Answer 6

they recognise abnormal bases by flipping the base out and cleaving them and this leaves an abasic site

Question 7

what will pol b do in dna repair

Answer 7

replace an abasic nt

Question 8

what is nucleotide excision repair and what triggers it

Answer 8

removal of oligonucleotide fragments from one strand
triggered by structural change

Question 9

what can ner repair

Answer 9

any kind of sequence damage

Question 10

what protein complex carries out ner in bacteria

Answer 10

UvrABC exonuclease

Question 11

how is ner carried out

Answer 11

uvrc and b will move along the DNA and cleave the fragment of dna

Question 12

what is mismatch repair

Answer 12

the detection and removal of incorrect base pairs

Question 13

how are mismatched pairs detected

Answer 13

a mismatched pair will distort the helix and will be detected by specialist proteins

Question 14

which base will be corrected in the mismatch repair

Answer 14

the daughter strand

Question 15

which protein will identify the daughter strand and cleave it

Answer 15

mutH

Question 16

which proteins will bind to the distortion

Answer 16

mutL/mutS complex

Question 17

what is the multi prong approach and what are the enzymes

Answer 17

the use of 3 different enzymes to prevent 8-oxo-G
mutT, mutM, mutY

Question 18

what is translesion synthesis

Answer 18

specialised polymerases that are able to continue duplicating despite there being damage on the DNA, will not stall

Question 19

how does homologous recombination work

Answer 19

while sister chromatids are still joined, the other can be used as a template for the other

Question 20

how does non-homologous end-joining work

Answer 20

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

Question 21

what does a defect in the ner mechanism form

Answer 21

xeroderma pigmentosum

Question 22

what does a defect in the mismatch repair mechanism cause

Answer 22

hereditary non-polyposis colon cancer