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FIRST AID > Biochem: molecular > Flashcards

Biochem: molecular Flashcards

1
Q

What histones make up the nuclosome core?

A

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

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2
Q

What amino acids are histones rich in?

A

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

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3
Q

Which histone beads the nucleosomes in a string?

A

H1

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4
Q

What does histone methylation lead to?

A

inactivates transcription of DNA

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5
Q

What does histone acetylation lead to?

A

relaxes DNA coiling, allows for transcription

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6
Q

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

A

adenine and cytosine

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

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7
Q

What turns cytosine into uracil?

A

deamination

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8
Q

What amino acids are needed for purine synthesis?

A

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

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9
Q

What is needed to make the pyrimidines?

A

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

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10
Q

What is the rate limiting step in pyrimidine synthesis?

A

CPSII

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11
Q

What enzyme does hydroxyurea inhibit?

A

ribonucleotide reductase

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12
Q

What enzyme does 6-MP inhibit?

A

glutamine PRPP amidotransferase

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13
Q

What enzyme does 5-FU inhibit?

A

thymidylate synthase (decreases dTMP)

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14
Q

What enzyme does MTX inhibit?

A

dehydrofolate reductase (decreases dTMP)

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15
Q

What does trimethoprim inhibit?

A

bacterial DHFR (decreases dTMP)

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16
Q

What causes orotic aciduria?

A

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

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17
Q

What are common findings in orotic aciduria patients?

A 
increased orotic acid in urine, megaloblastic anemia that does not imporve with B12/folate, failture to thrive
NO hyperammonemia (vs OTC deficiency)
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18
Q

How is orotic aciduria treated?

A

oral uridine administration

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19
Q

What is the result of adenosine deaminase deficiency?

A

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

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20
Q

What disease can adenosine deaminase deficiency cause?

A

SCID

AR

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21
Q

What happens when the enzyme HGPRT is deficient/absent?

A

defective purine salvage

results in excess uric acid production and de novo purine synthesis

22
Q

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

A

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

23
Q

What is Lesch Nyhan treated with?

A

allopurinol

24
Q

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

A

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

25
Q

What type of lesion does nucleotide excision repair repair?

A

bulky helix distorting lesions

26
Q

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

A

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

27
Q

What repair mechanism is damaged in HNPCC?

A

mismatch repair

28
Q

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

A

non homologous end joining (fixes double stranded breaks)

29
Q

Which direction is mRNA read?

A

5’ —> 3’

30
Q

What direction is protein synthesized?

A

N-terminus to C terminus

31
Q

What does DNA pol a do?

A

replicates lagging strand and synthesizes RNA primer

32
Q

What does DNA pol B do?

A

repairs DNA

33
Q

What does DNA pol g do?

A

replicates mitochondrial DNA

34
Q

What does DNA pol d do?

A

replicates leading strand

35
Q

What causes bloom syndrome?

A

mutation of helicase

affects DNA replication and repair

36
Q

Which RNA pol synthesizes rRNA? Where does this occur?

A

I

in nucleolus

37
Q

Which RNA pol synthesizes mRNA? What inhibits it?

A 
II
alpha amantin (mushroom toxin)
38
Q

Which RNA pol synthesizes tRNA?

A

III

39
Q

What is the mRNA start codon?

A

AUG

40
Q

What are the mRNA stop codons?

A

UGA, UAA, UAG

41
Q

Where is the TATA box located?

A

promotor region

42
Q

What symptom is seen if a amantin is ingested?

A

hepatotoxicity

43
Q

What inhibits prokaryotic RNA polymerase?

A

rifampin

44
Q

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

A

5’ end

needs SAM

45
Q

Where does the poly A tail go?

A

3’ end

46
Q

What is the polyadenylation signal?

A

AAUAAA

47
Q

What are patients with lupus making antibodies against?

A

spliceosomal snRNPs

48
Q

Which part of the mRNA contains the actual genetic information?

A

exons (introns are spliced out)

49
Q

Where do amino acids attach to tRNA?

A

3’ end

CCA

50
Q

What charges tRNA?

A

aminoacyl tRNA synthetase

51
Q

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

A

EF-G prokaryotes

EF-2 eukaryotes

52
Q

What are the three main categories of posttranslational modifications?

A

trimming
covalent alterations
proteasomal degradation

FIRST AID (8 decks)

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