genomic regulation

Question 1

3 nucleoside analog inhibitors

Answer 1

ara-C (cytarabine) becomes ara-CTP and inhibits DNA polymerase. treats leukemia.

acyclovir (gets phosphorylated by host) and AZT (treats HIV) both lack 3’ OH group so they arrest viral DNA synthesis by acting as chain terminators.

Question 2

if CpG islands in promoter are methylated…

Answer 2

silences genes.

if this happens to gonads/sperm, methylation is passed on to progeny.

often methylated due to stress

Question 3

cross linking agents (cross link DNA and protein)

Answer 3

nitrogen mustard, cisplatin, mitomycin C, carmustine

Question 4

alkylating agents (denature DNA)

Answer 4

dimethyl sulfate (DMS), methyl methanesulfonate (MMS)

Question 5

intercalating agents (break NA through adding structural change)

Answer 5

thalidomide

Question 6

direct repair

Answer 6

• repairs pyrimidine dimers and O6 methylguanine

- uses DNA photolyase and methylguanine methyltransferase

Question 7

base excision repair

Answer 7

• repairs single base mismatches or depurination

- uses DNA glycosylase, AP endonuclease, DNA pol, AP lyase, DNA ligase

Question 8

nucleotide excision repair

Answer 8

• repairs chemical adducts that distort DNA (ex. pyr dimers)
• uses NER protein complex, DNA pol, DNA ligase
• ->Xeroderma pigmentosum

Question 9

mismatch excision repair

Answer 9

• repairs mismatched base in daughter strand
• uses MER complex (MutS and MutL), helicase/endonuclease, DNA pol, DNA ligase
• ->Hereditary nonpolyposis colorectal cancer

Question 10

recombination repair

Answer 10

-repairs double stand breaks, interstrand cross linking (nonhomologous end joining, homologous recombination)

• NHEJ: with damaged ends filled/joined, DNA ligase
• homologous recombo: w/ exonucleases, DNA pol, MER (uses info from normal DNA pair to fix)

–>BRCA mutations and breast cancer

Question 11

transcription-couples repair

Answer 11

• repairs stalled RNA pol during transcription

- ->Cockayne syndrome

Question 12

translesion synthesis (bypass synthesis)

Answer 12

• repairs unrepaired thymine dimers or apurinic AP sites

- uses DNA pol

Question 13

inhibitors of Histone deacetylases

Answer 13

valproic acid, vorinostat

Question 14

what does rifampicin do?

Answer 14

• inhibits bacterial RNA synthesis
• side effects: increases hepatic cytochrome P-450 enzymes (they add OH to make drugs more soluble, they metabolize drugs), thus increasing metabolism of other drugs and hormones. RED COLOR in urine, sweat, tears for a short time.

Question 15

imprinting

Answer 15

when methylation/non-methylation can be passed down (think CpG islands)