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step 1 - biochem > molecular > Flashcards

molecular Flashcards

1
Q

which AAs are in histones?

A

lysine

arginine

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2
Q

what is H1?

A

linker protein

binds histone, nucleosome, linker DNA - stabilizes chromatin

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3
Q

what does DNA methylation do?

A

template strand methylation of C and A –> mismatch repair can tell old from new
CpG island methylation –> represses transcription

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4
Q

what does histone methylation do?

A

represses transcription

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5
Q

what does histone acetylation do?

A

relaxes DNA coiling –> activates transcription

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6
Q

which AAs are necessary for purine synthesis?

A

GAG
glycine
aspartate
glutamine

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7
Q

which AAs are necessary for pyrimidine synthesis?

A

aspartate

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8
Q

what does leflunomide do?

A

inhibits dihydroorotate synthesis - prevents formation of orotic acid in pyrimidine synth pathway

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9
Q

what do mycophenolate and ribavirin do?

A

inhibit IMP DH in GMP synthesis - end of purine synth pathway

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10
Q

what does hydroxyurea do?

A

inhibits ribonucleotide reductase - part of pyrimidine synth pathway

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11
Q

what does 6MP/azathioprine do?

A

inhibit de novo purine synthesis

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12
Q

what does 5FU do?

A

inhibits thymidylate synthase –> decreased dTMP

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13
Q

what do methotrexate, TMP, and pyrimethamine do?

A

inhibit dihydrofolate reductase (species specific - MTX in humans, TMP in bacteria, pyrimethamine in protozoa)
- decreased dTMP

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14
Q

what does probenecid do?

A

increases uric acid excretion in urine

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15
Q

what do allopurional and febuxostat do?

A

block xanthine oxidase –> prevent build up of uric acid

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16
Q

AR cause of SCID?

A

adenosine deaminase deficiency

imbalance of nucleotide pool –> DNA synth prevented

17
Q

intellectual disability, self-mutilation, aggression, dystonia, hyperuricemia, gout?

A

Lesch-Nyhan, XLR
HPGRT absent
excess hypoxanthine and guanine –> excess uric acid prodcution and excess DE NOVO purine synthesis

tx: allopurinol or febuxostat

18
Q

what proofreader function does DNA pol III have?

A

3’-5’ exonuclease

19
Q

what functions does DNA pol I have?

A

same as DNA pol III + RNA 5’-3’ exonuclease

20
Q

what substitution is made in sickle cell dz?

A

glutamate –> valine

21
Q

what is the fn of glucose in the lac operon?

A

low glu –> increased cAMP –> activation of CAP –> transcription induction

22
Q

what is the fn of lactose in the lac operon?

A

high lactose –> repressor removed from operator site –> transcription

23
Q

what DNA repair process is deficient in xeroderma pigmentosum?

A

nucleotide excision repair (G1)

24
Q

what DNA repair process is deficient in HNPCC?

A

mismatch repair (G2)

25
Q

what DNA repair process is deficient in ataxia telangiectasia and Fanconi anemia?

A

dsDNA break repair - nonhomologous end joining

26
Q

what are the mRNA stop codons?

A

UGA - u go away
UAA - u are away
UAG - u are gone

27
Q

what does RNA pol I do?

A

makes rRNA

most numerous

28
Q

what does RNA pol II do? what inhibits it?

A

makes mRNA
opens DNA at promoter
largest
inhibited by alpha-amanitin (mushrooms) –> hepatotoxicity

29
Q

what does RNA pol III do?

A

tRNA

smallest

30
Q

what are post-transcriptional modifications of hnRNA?

A

capping
polyadenylation
splicing
–> mRNA

31
Q

what are cytoplasmic P bodies?

A

mRNA quality control

exonucleases, decapping enzymes, miRNA

32
Q

which are auto-Abs to snRNPs?

A

anti-Smith

anti-U1 RNP

33
Q

what sequence do AAs bind on tRNA?

A

CCA at 3’ end

34
Q

what sequence is in the T arm of tRNA?

A

thymine pseudouracil cytosine

necessary to bind ribosome

35
Q

what is in the D arm of tRNA?

A

dihydrouracil

needed for recognition by aminoacyl-tRNA synthetase

36
Q

which are the eukaryotic ribosome subunits?

A

40s, 60s –> 80s

37
Q

which are the prokaryotic ribosome subunits?

A

30s, 50s –> 70s

38
Q

what are initiation factors?

A

help assemble 40s subunit, released when mRNA and 60s assemble

39
Q

what is fMet?

A

translation of start codon in prokaryotes

stimulates neutrophil chemotaxis

step 1 - biochem (5 decks)

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