Biochem: molecular

Question 1

What histones make up the nuclosome core?

Answer 1

H2A, H2B, H3, H4 (2 of each)

Question 2

What amino acids are histones rich in?

Answer 2

lysine and ariginine, they give positive charge, bind negatively charged DNA

Question 3

Which histone beads the nucleosomes in a string?

Answer 3

H1

Question 4

What does histone methylation lead to?

Answer 4

inactivates transcription of DNA

Question 5

What does histone acetylation lead to?

Answer 5

relaxes DNA coiling, allows for transcription

Question 6

Which DNA bases are methylated? What purpose does this serve?

Answer 6

adenine and cytosine

allows mistmatch repair enzymes to distinguish between old and new strands in prokaryotes

Question 7

What turns cytosine into uracil?

Answer 7

deamination

Question 8

What amino acids are needed for purine synthesis?

Answer 8

glycine
aspartate (N)
glutamate (N)
(also need tetrahydrofolate and CO2)

Question 9

What is needed to make the pyrimidines?

Answer 9

aspartate, carbamoyl phosphate-made of CO2, glutamine, ATP

Question 10

What is the rate limiting step in pyrimidine synthesis?

Answer 10

CPSII

Question 11

What enzyme does hydroxyurea inhibit?

Answer 11

ribonucleotide reductase

Question 12

What enzyme does 6-MP inhibit?

Answer 12

glutamine PRPP amidotransferase

Question 13

What enzyme does 5-FU inhibit?

Answer 13

thymidylate synthase (decreases dTMP)

Question 14

What enzyme does MTX inhibit?

Answer 14

dehydrofolate reductase (decreases dTMP)

Question 15

What does trimethoprim inhibit?

Answer 15

bacterial DHFR (decreases dTMP)

Question 16

What causes orotic aciduria?

Answer 16

inability to convert orotic acid to UMP because of AR defect in UMP synthase

Question 17

What are common findings in orotic aciduria patients?

Answer 17

increased orotic acid in urine, megaloblastic anemia that does not imporve with B12/folate, failture to thrive
NO hyperammonemia (vs OTC deficiency)

Question 18

How is orotic aciduria treated?

Answer 18

oral uridine administration

Question 19

What is the result of adenosine deaminase deficiency?

Answer 19

excess ATP and dATP imbalances nucleotide pool which prevents DNA synthesis
this decreases lymphocyte count

Question 20

What disease can adenosine deaminase deficiency cause?

Answer 20

SCID

AR

Question 21

What happens when the enzyme HGPRT is deficient/absent?

Answer 21

defective purine salvage

results in excess uric acid production and de novo purine synthesis

Question 22

What disease is caused by HGPRT deficiency? Sx? Inheritance?

Answer 22

Lesch Nyhan
XR
retardation, self mutilation, aggression, hyperuricemia, gout, choreoathetosis

Question 23

What is Lesch Nyhan treated with?

Answer 23

allopurinol

Question 24

What DNA repair machanism is mutated in xeroderma pigmentosa? what does this prevent?

Answer 24

nucleotide excision repair (endonucleases)
can’t repair pyrimidine dimers
increased risk of skin cancer

Question 25

What type of lesion does nucleotide excision repair repair?

Answer 25

bulky helix distorting lesions

Question 26

What type of lesion does base excision repair fix? What does it need to do this?

Answer 26

repairs spontaneous/toxic deamination (repairs damaged bases) needs glycosylases

Question 27

What repair mechanism is damaged in HNPCC?

Answer 27

mismatch repair

Question 28

What type of DNA repair is non functioning in ataxia telangiectasia?

Answer 28

non homologous end joining (fixes double stranded breaks)

Question 29

Which direction is mRNA read?

Answer 29

5' ---> 3'

Question 30

What direction is protein synthesized?

Answer 30

N-terminus to C terminus

Question 31

What does DNA pol a do?

Answer 31

replicates lagging strand and synthesizes RNA primer

Question 32

What does DNA pol B do?

Answer 32

repairs DNA

Question 33

What does DNA pol g do?

Answer 33

replicates mitochondrial DNA

Question 34

What does DNA pol d do?

Answer 34

replicates leading strand

Question 35

What causes bloom syndrome?

Answer 35

mutation of helicase | affects DNA replication and repair

Question 36

Which RNA pol synthesizes rRNA? Where does this occur?

Answer 36

I | in nucleolus

Question 37

Which RNA pol synthesizes mRNA? What inhibits it?

Answer 37

``` II alpha amantin (mushroom toxin) ```

Question 38

Which RNA pol synthesizes tRNA?

Answer 38

III

Question 39

What is the mRNA start codon?

Answer 39

AUG

Question 40

What are the mRNA stop codons?

Answer 40

UGA, UAA, UAG

Question 41

Where is the TATA box located?

Answer 41

promotor region

Question 42

What symptom is seen if a amantin is ingested?

Answer 42

hepatotoxicity

Question 43

What inhibits prokaryotic RNA polymerase?

Answer 43

rifampin

Question 44

Where does the methyguanine cap go? What cofactor is required?

Answer 44

5' end | needs SAM

Question 45

Where does the poly A tail go?

Answer 45

3' end

Question 46

What is the polyadenylation signal?

Answer 46

AAUAAA

Question 47

What are patients with lupus making antibodies against?

Answer 47

spliceosomal snRNPs

Question 48

Which part of the mRNA contains the actual genetic information?

Answer 48

exons (introns are spliced out)

Question 49

Where do amino acids attach to tRNA?

Answer 49

3' end | CCA

Question 50

What charges tRNA?

Answer 50

aminoacyl tRNA synthetase

Question 51

What does translocation during protein synthesis requrie in prokaryotes? eukaryotes?

Answer 51

EF-G prokaryotes | EF-2 eukaryotes

Question 52

What are the three main categories of posttranslational modifications?

Answer 52

trimming covalent alterations proteasomal degradation