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Step 1 - Biochemistry > Molecular > Flashcards

Molecular Flashcards

1
Q

Nucleosome

A

Histone octamer:

H2A, H2B, H3, H4 x 2

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2
Q

Beads on a string

A

Negatively charged DNA loops twice around positively charged histone octamer

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3
Q

Histones are rich in which Aa?

A

Lysine

Arginine

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4
Q

H1 binds to

A

Nucleosome

Linker DNA

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5
Q

DNA and Histone synthesis occurs during what phase of the cell cycle?

A

S phase

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6
Q

Highly condensed cromatin, transcriptionally inactive

A

Heterocromatin

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7
Q

Barr bodies

A

Inactive X chromosomes in heterochromatin

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8
Q

Less condensed cromatin, transcriptionally active

A

Eucromatin

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9
Q

Methylation of DNA cytosin and adenin

A

Methylation of template strands for mismatch repair enzymes to distinguish old and new strands

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10
Q

Methylation at CpG islands

A

Represses transcription

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11
Q

Histone acetylation

A

Relaxes DNA coiling, allowing for transcription

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12
Q

Histone methylation

A

Reversibly represses DNA trasncription

sometimes it activates it depending on location

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13
Q

NucleoSide

A

Base + (desoxy)ribose (Sugar)

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14
Q

NucleoTide

A

Base + (desoxy)ribose+phosphaTe linked by 3’-5’ phosphodiester bond

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15
Q

Purines

A

Adenine
Guanine
PURe As Gold

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16
Q

Pyrimidines

A

Citosine
Uracil
Thymine
CUT the PYe

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17
Q

Deamination of citosine

A

Uracil

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18
Q

Deamination of adenine

A

Guanine

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19
Q

methylation of uracil

A

Thymine

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20
Q

5’ end of nucleotide bears

A

Triphosphate

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21
Q

Target of 3’ hydroxyl attack

A

Triphosphate bond

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22
Q

A-T or C-G: stronger bond

A

C-G: 3 H bonds

A-T: 2 H bonds

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23
Q

Rises melting temperature of DNA

A

Higher number of C-G bonds (strong)

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24
Q

Amino acids necessary for purine synthesis

A

Glycine
Aspartate
Glutamine

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25
Q

Disrupt pyrimidine synthesis

A
  1. Leflunomide
  2. MTX
  3. Trimethoprim
  4. Pyrimethamine
  5. 5-FU
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26
Q

Leflunomide: action

A

Disrupt pyrimidine synthesis: inhibits dihydroorotate dehydrogenase

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27
Q

MTX: action

A

Disrupt pyrimidine synthesis: inhibits dihydrofolate reductase in humans: less TMP

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28
Q

Trimethoprim: action

A

Disrupt pyrimidine synthesis: inhibits dihydrofolate reductase in humans: less TMP

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29
Q

Pyrimethamine: action

A

Disrupt pyrimidine synthesis: inhibits dihydrofolate reductase in protozoa: less dTMP

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30
Q

Disrupt purine synthesis

A
  1. 6 Mercaptopurine and azathioprine (prodrug)
  2. Mycophenolate
  3. Ribavirin
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31
Q

Disrupts purine and pyrimidine synthesis

A

Hydroxiurea: inhibits rybonucleotide reductase

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32
Q

5-FU action

A

Inhibits thymidylate synthase: less dTMP

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33
Q

Allopurinol and Febuxostat: action

A

Inhibit Xanthine oxidase to produce less Uric Acid

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34
Q

Probenecid action

A

Increases conversion of uric acid to urine

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35
Q

One of the major causes of autosomal recessive SCID

A

Adenosine deaminase deficiency

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36
Q

Effects of Adenosine deaminase deficiency

A

dATP accumulates, which is toxic for lymphocytes

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37
Q

Lesch-Nyhan syndrome: cause

A

Defective purine salvage due to absence of HGPRT: excess uric acid and de novo purine synthesis

38
Q

Lesch-Nyhan syndrome: heritability

A

X-linked Recessive

39
Q

Findings in Lesch-Nyhan syndrome

A

HGPRT

  • Hyperuicemia
  • Gout
  • Pissed off: aggresion, self-mutilation
  • Retardation
  • DysTonia
40
Q

Treatment for Lesch-Nyhan syndrome

A

Allopurinol

Febuxostat

41
Q

Genetic code features

A
  1. Unambiguous
  2. Degenerate/redundant
  3. Commaless, nonoverlapping
  4. Universal
42
Q

Wobble

A

Codons that differ in 3rd wobble position may code for the same tRNA/Amino acid

43
Q

DNA replication is

A

Semiconservative
Involves continous and discontinuous synthesis
5’–>3’ direction

44
Q

Okazaki fragment

A

Discontinuous DNA synthesis

45
Q

Origin of replication

A

COnsensus sequence of base pairs in genomewhere DNA replication begins

46
Q

Helicase: function

A

Unwinds DNA template at replication fork

47
Q

Single-stranded binding proteins

A

Prevent strands from reannealing

48
Q

DNA topoisomerases: function

A

Create a break in the helix to add or remove supercoils

49
Q

Irinotecan inhibits

A

Eukariotic topoisomerase I

50
Q

Etoposide inhibits

A

Eukaryotic topoisomerase II

51
Q

Fluoroquinolones function

A

Inhibit prokaryotic topoisomerase II (girase) and IV

52
Q

Primase function

A

Makes an RNA primer on which DNA polymerase III can initiate replication

53
Q

DNA polymerase III function

A

5–3 synthesis

Proofreads 3–5 exonuclease

54
Q

DNA polymerase I function

A

Degrades RNA primer and replaces it with DNA

55
Q

Joins Okazaki fragments

A

DNA ligase

56
Q

Transition mutation

A

Purine to purine

Pyrimidine to pyrimidine

57
Q

Transversion mutation

A

Purine to Pyrimidine

Pyrimidine to purine

58
Q

Silent mutation

A

Nucleotide substitution but codes for the same synonymous amino acid

59
Q

Missense mutation

A

Nucleotide substitution resulting in changed aminoacid

60
Q

Sickle cell disease: mutatino

A

Missense mutation: substitution of glutamic acid with valine

61
Q

Nucleotide substitution results in early stop codon: UAG, UGA, UAA

A

Nonsense mutation

62
Q

Examples of diseases caused by a frameshift mutation

A

Duchenne muscular dystrophy

Tay Sachs disease

63
Q

Classic example of genetic response to environmental change

A

Lac operon

64
Q

Defective in xeroderma pigmentosum

A

Nucleotide excision repair

65
Q

Nucleotide excision repair occurs in

A

G1 phase of cell cycle

66
Q

Base excision repair

A 
Glycosilase removes altered base
AP-Endonuclease
Lyase
DNA polymerase beta
Ligase
67
Q

Defective in Lynch Syndrome

A

Mismatch repair

68
Q

Defective nonhomologous end joining

A

Fanconi anemia
Ataxia telangectasia
BRCA1 cancers

69
Q

Site where positive regulators bind

A

Enhancer

70
Q

Site where negative regulators bind

A

Silencer

71
Q

RNA polymerases

A

I: rRNA
II: mRNA
III: tRNA
In the order that their products are used in protein synthesis

72
Q

Amanita phalloides alfa-amantin effect

A

Inhibits RNA polymerase II

73
Q

Actinomycin D inhibits

A

RNA polymerase

74
Q

Rifampicin inhibits

A

RNA polymerase in prokariotes

75
Q

mRNA is translated in

A

Cytosol

76
Q

hnRNA processes that yield mRNA

A
  • Capping of 5’ end: methylguanosine cap
  • Polyadenilation of 3’ end 200A
  • Splicing out of introns
77
Q

mRNA quality control

A

Processing bodies (P-bodies)

78
Q

Polyadenilation signal

A

AAUAAA

79
Q

Highly specific antibodies for SLE

A

snRNP

80
Q

Anti-U1 RNP antibodies

A

Mixed connective tissue disease (MCTD)

81
Q

Spliceosome

A

Primary transcript mRNA combines with snRNP and other proteins

82
Q

Lariat intermediate is released to

A

Intron and join 2 exons

83
Q

Introns stay

A

In the nucleus

84
Q

microRNA function

A

noncoding RNA that posttranscriptionallty regulate gene expression by targeting 3’ untranslated region of mRNA for degradation or translational repression

85
Q

Amino acid is covalently bound to what end of the tRNA

A

3’ end CCA extrem: Can carry aminoacids

86
Q

Aminoacyl tRNA synthetase function

A

Binds specific aminoacid to specific tRNA

87
Q

Eukariotic ribosome

A 
40+60= 80S 
Eukariotic= Even
88
Q

PrOkariotic ribosome

A

30S+50S= 70S

PrOkariotic=Odd

89
Q

Protein synthesis occours from__-terminal to ____-terminal

A

N to C

90
Q

Ribosome sites

A

APE
A: incoming Aminoacyl-RNA
P: accomodates growing Peptide
E: holes Empty tRNA as it exits

91
Q

Trimming a protein

A

Removal of N or C terminal propeptides from zymogen to generate mature protein

92
Q

Intracellular protein involved in maintaining protein fold

A

Chaperone protein

Step 1 - Biochemistry (7 decks)

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