Biochem

Question 1

What drug inhibits dihydroorotate dehydrogenase?

Answer 1

Leflunomide (de novo pyrimidine synth)

Question 2

What drugs inhibit IMP dehydrogenase?

Answer 2

Mycophenolate (immunosuppressant used in solid organ transplant), ribavirin (RSV, HCV)
(de novo purine synthesis –> inhibits GMP synthesis)

Question 3

What drugs inhibit de novo purine synthesis (PRPP –> IMP)?

Answer 3

6-MP, azathioprine [used in NHL, PCV, IBD, etc.]

Question 4

What drugs inhibit dihydrofolate reductase?

Answer 4

MTX, TMP, pyrimethamine (pyrimidine synthesis)

Question 5

What drug inhibits thymidylate synthase?

Answer 5

5-FU (used to tx cancer)

Question 6

Which enzyme involved in DNA replication can excise RNA primer in the 5’–>3’ direction?

Answer 6

DNA pol I

and NOT III

Question 7

What class of abx inhibit DNA gyrase (prokaryotic topoisomerase II)?

Answer 7

fluoroquinolones

Question 8

What enzyme is defective in xeroderma pigmentosum?

Answer 8

endonuclease (nucleotide excision repair); inability to repair pyrimidine dimers that form with UV exposure

Question 9

What function is defective in HNPCC?

Answer 9

DNA mismatch repair (take out wrong base)

Question 10

What function is screwed up in ataxia telangiectasia?

Answer 10

nonhomologous end joining (secondary to double-stranded breaks)

Question 11

DNA and RNA synthesis occur in the ??? direction

Answer 11

5’ –> 3’

Question 12

mRNA is read in the ??? direction

Answer 12

5’ –> 3’

Question 13

Protein synthesis is ???-terminus to ???-terminus

Answer 13

N to C

Question 14

start codon

Answer 14

AUG (methionine in euk and f-met in prok)

AUG inAUGurates protein synthesis

Question 15

stop codons

Answer 15

UGA, UAA, UAG

NB: these do NOT code for an aa; last aa in protein = codon prior to stop codon

Question 16

How many types of eukaryotic RNA polymerases are there?

Answer 16

3

Question 17

How many types of prokaryotic RNA polymerases are there?

Answer 17

1

Question 18

How many types of prokaryotic DNA polymerases are there?

Answer 18

3

Question 19

How many types of eukaryotic DNA polymerases are there?

Answer 19

1

Question 20

euk RNA pol I makes ???

Answer 20

rRNA (rampant)

Question 21

euk RNA pol II makes ???

Answer 21

mRNA (massive)

Question 22

euk RNA pol III makes ???

Answer 22

tRNA (tiny)

Question 23

polyadenylation signal

Answer 23

AAUAAA

polyA polymerase does NOT require a template

Question 24

What regulates mRNA quality control?

Answer 24

cytoplasmic P-bodies

Question 25

What diseases have antibodies to snRNPs?

Answer 25

SLE (“anti-smith”)

Question 26

tRNA CCA

Answer 26

can carry amino acids; found at 3’ end

Question 27

going APE

Answer 27

A site = incoming Aminoacyl-tRNA
P site = accommodates growing Peptide
E site = holds Empty tRNA as it Exits