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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
Disrupt pyrimidine synthesis
1. Leflunomide 2. MTX 3. Trimethoprim 4. Pyrimethamine 5. 5-FU
26
Leflunomide: action
Disrupt pyrimidine synthesis: inhibits dihydroorotate dehydrogenase
27
MTX: action
Disrupt pyrimidine synthesis: inhibits dihydrofolate reductase in humans: less TMP
28
Trimethoprim: action
Disrupt pyrimidine synthesis: inhibits dihydrofolate reductase in humans: less TMP
29
Pyrimethamine: action
Disrupt pyrimidine synthesis: inhibits dihydrofolate reductase in protozoa: less dTMP
30
Disrupt purine synthesis
1. 6 Mercaptopurine and azathioprine (prodrug) 2. Mycophenolate 3. Ribavirin
31
Disrupts purine and pyrimidine synthesis
Hydroxiurea: inhibits rybonucleotide reductase
32
5-FU action
Inhibits thymidylate synthase: less dTMP
33
Allopurinol and Febuxostat: action
Inhibit Xanthine oxidase to produce less Uric Acid
34
Probenecid action
Increases conversion of uric acid to urine
35
One of the major causes of autosomal recessive SCID
Adenosine deaminase deficiency
36
Effects of Adenosine deaminase deficiency
dATP accumulates, which is toxic for lymphocytes
37
Lesch-Nyhan syndrome: cause
Defective purine salvage due to absence of HGPRT: excess uric acid and de novo purine synthesis
38
Lesch-Nyhan syndrome: heritability
X-linked Recessive
39
Findings in Lesch-Nyhan syndrome
HGPRT - Hyperuicemia - Gout - Pissed off: aggresion, self-mutilation - Retardation - DysTonia
40
Treatment for Lesch-Nyhan syndrome
Allopurinol | Febuxostat
41
Genetic code features
1. Unambiguous 2. Degenerate/redundant 3. Commaless, nonoverlapping 4. Universal
42
Wobble
Codons that differ in 3rd wobble position may code for the same tRNA/Amino acid
43
DNA replication is
Semiconservative Involves continous and discontinuous synthesis 5'-->3' direction
44
Okazaki fragment
Discontinuous DNA synthesis
45
Origin of replication
COnsensus sequence of base pairs in genomewhere DNA replication begins
46
Helicase: function
Unwinds DNA template at replication fork
47
Single-stranded binding proteins
Prevent strands from reannealing
48
DNA topoisomerases: function
Create a break in the helix to add or remove supercoils
49
Irinotecan inhibits
Eukariotic topoisomerase I
50
Etoposide inhibits
Eukaryotic topoisomerase II
51
Fluoroquinolones function
Inhibit prokaryotic topoisomerase II (girase) and IV
52
Primase function
Makes an RNA primer on which DNA polymerase III can initiate replication
53
DNA polymerase III function
5--3 synthesis | Proofreads 3--5 exonuclease
54
DNA polymerase I function
Degrades RNA primer and replaces it with DNA
55
Joins Okazaki fragments
DNA ligase
56
Transition mutation
Purine to purine | Pyrimidine to pyrimidine
57
Transversion mutation
Purine to Pyrimidine | Pyrimidine to purine
58
Silent mutation
Nucleotide substitution but codes for the same synonymous amino acid
59
Missense mutation
Nucleotide substitution resulting in changed aminoacid
60
Sickle cell disease: mutatino
Missense mutation: substitution of glutamic acid with valine
61
Nucleotide substitution results in early stop codon: UAG, UGA, UAA
Nonsense mutation
62
Examples of diseases caused by a frameshift mutation
Duchenne muscular dystrophy | Tay Sachs disease
63
Classic example of genetic response to environmental change
Lac operon
64
Defective in xeroderma pigmentosum
Nucleotide excision repair
65
Nucleotide excision repair occurs in
G1 phase of cell cycle
66
Base excision repair
``` Glycosilase removes altered base AP-Endonuclease Lyase DNA polymerase beta Ligase ```
67
Defective in Lynch Syndrome
Mismatch repair
68
Defective nonhomologous end joining
Fanconi anemia Ataxia telangectasia BRCA1 cancers
69
Site where positive regulators bind
Enhancer
70
Site where negative regulators bind
Silencer
71
RNA polymerases
I: rRNA II: mRNA III: tRNA In the order that their products are used in protein synthesis
72
Amanita phalloides alfa-amantin effect
Inhibits RNA polymerase II
73
Actinomycin D inhibits
RNA polymerase
74
Rifampicin inhibits
RNA polymerase in prokariotes
75
mRNA is translated in
Cytosol
76
hnRNA processes that yield mRNA
- Capping of 5' end: methylguanosine cap - Polyadenilation of 3' end 200A - Splicing out of introns
77
mRNA quality control
Processing bodies (P-bodies)
78
Polyadenilation signal
AAUAAA
79
Highly specific antibodies for SLE
snRNP
80
Anti-U1 RNP antibodies
Mixed connective tissue disease (MCTD)
81
Spliceosome
Primary transcript mRNA combines with snRNP and other proteins
82
Lariat intermediate is released to
Intron and join 2 exons
83
Introns stay
In the nucleus
84
microRNA function
noncoding RNA that posttranscriptionallty regulate gene expression by targeting 3' untranslated region of mRNA for degradation or translational repression
85
Amino acid is covalently bound to what end of the tRNA
3' end CCA extrem: Can carry aminoacids
86
Aminoacyl tRNA synthetase function
Binds specific aminoacid to specific tRNA
87
Eukariotic ribosome
``` 40+60= 80S Eukariotic= Even ```
88
PrOkariotic ribosome
30S+50S= 70S | PrOkariotic=Odd
89
Protein synthesis occours from__-terminal to ____-terminal
N to C
90
Ribosome sites
APE A: incoming Aminoacyl-RNA P: accomodates growing Peptide E: holes Empty tRNA as it exits
91
Trimming a protein
Removal of N or C terminal propeptides from zymogen to generate mature protein
92
Intracellular protein involved in maintaining protein fold
Chaperone protein

Step 1 - Biochemistry (7 decks)

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