DNA Repair

Question 1

Specific endonucleases release the oligonucleotides containing damaged bases

DNA polymerase - fill
DNA ligase - reseal

repairs bulky helix distorting lesions

Answer 1

NUCLEOTIDE EXCISION REPAIR

G1 phase

defective in XERODERMA PIGMENTOSUM
(inability to repair DNA pyrimidine dimers caused by UV exposure)
*dry skin
*extreme light sensitivity
*skin cancer

Question 2

Base specific GLYCOSYLASE removes altered base and creates AP site

Answer 2

BASE EXCISION REPAIR

important in repair of spontaneous/toxic deamination

Question 3

Mismatched nucleotides in newly synthesized (unmethylated) strand are removed and gap is filled and released

Answer 3

MISMATCH REPAIR

S PHASE

defective in LYNCH SYNDROME (HNPCC)

Question 4

Brings together 2 ends of DNA fragments to repair double stranded breaks

Answer 4

NONHOMOLOGOUS END JOINING

defective in ATAXIA TELANGIECTASIA

Question 5

Requires 2 homologous DNA duplexes

Answer 5

HOMOLOGOUS RECOMBINATION

defective in BREAST/OVARIAN CANCERS w/ BRCA1 mutation and in FANCONI ANEMIA