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Biochemistry > Exam #4 First Aid USMLE > Flashcards

Exam #4 First Aid USMLE Flashcards

1
Q

H1

A
  • Histone that binds to the nucleosome & linker DNA

- Only Histone not in the nucleosome core

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2
Q

When does DNA & Histone synthesis occur in the cell cycle?

A

S-phase

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3
Q

Nucleosome Core Histones

A
  • H2A
  • H2B
  • H3
  • H4
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4
Q

Heterochromatin

A
  • Highly Condensed & Inactive

- Think HeteroChromatin, Highly Condensed

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5
Q

Euchromatin

A
  • Less condensed, transcriptionally active, sterically accessible
  • Think Eu= True, truly transcribed
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6
Q

DNA Methylation

A
  • Methylation at CpG islands represses transcription

- Think Methylation Makes DNA Mute

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7
Q

Histone Acetylation

A
  • Relaxes DNA coiling, allowing for transcription

- Think Acetylation makes DNA Active

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8
Q

What is the production of cytosine deamination?

A

Uracil

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9
Q

DNA Replication Characteristics

A
  • Semiconservative

- Involves BOTH continuous & discontinuous synthesis

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10
Q

Origin of Replication

A
  • Consensus sequence in genome where DNA replication begins

- Single in prokaryotes, Multiple in eukaryotes

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11
Q

Replication Fork

A
  • Y-shaped region along DNA template where leading & lagging strands are synthesized
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12
Q

Helicase

A

Unwinds DNA

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13
Q

Single-stranded binding proteins

A

Prevents strands from reannealing

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14
Q

Topoisomerases

A

Create single or double strand break in helix to relieve supercoiling

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15
Q

Fluoroquinolones

A

Inhibit DNA gyrase i.e. prokaryotic topoisomerase II

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16
Q

Primase

A

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

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17
Q

DNA Ligase

A
  • Catalyzes the formation of phosphodiester bonds within ds-DNA
  • Seals or joins Okazaki fragments
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18
Q

Telomerase

A

RNA-dependent DNA polymerase that adds DNA to 3’ ends of chromosomes to avoid loss of genetic material during replication

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19
Q

Silent Mutation

A

Nucleotide substitution codes for the same amino acid

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20
Q

Missense Mutation

A
  • Nucleotide substitution results in different amino acid

- Sickle Cell Disease

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21
Q

Nonsense Mutation

A
  • Nucleotide substitution results in an early STOP codon

- Think STOP the Nonsense

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22
Q

Frameshift Mutation

A
  • Insertion or deletion of nucleotides not divisible by 3 causing a misreading of DNA downstream
  • Duchenne Muscular Dystrophy
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23
Q

Nucleotide Excision Repair

A
  • Repairs bulky helex distorting lesions e.g. pyrimidine dimers from UV exposure
  • Endonucleases release an oligonucleotide containing damaged bases
  • DNA polymerase & ligase fill and reseal the gap
24
Q

Xeroderma Pigementosum

A

Defective Nucleotide Excision Repair

25
Base Excision Repair
- Important repair for spontaneous/ toxic deamination - Base-specific glyocsylase recognizes altered base & creates AP site - AP-endonuclease & Lyase cleave - DNA polymerase fills in the gap & Ligase seals it
26
Mismatch Repair
- Newly synthesized DNA strand is recognized - Mismatched nucleotides are removed - Gap is filled & resealed
27
HNPCC
Defective Mismatch Repair
28
Nonhomologous End Joining
- Brings together 2 ends of DNA fragments to repair ds-DNA breaks
29
Ataxia Telangiectasia
Nonhomologous End Joining
30
DNA & RNA Synthesis
- 5'-->3' | - 5' end of incoming nucleotide bears triphosphate energy source
31
Protein Synthesis
N-terminus to C-terminus
32
mRNA START Codon
- AUG - Think AUG inAUGurates protein synthesis - Codes for methionine, which may be removed before translation is completed
33
mRNA STOP Codons
- UGA= U Go Away - UAA= U Are Away - UAG= U Are Gone
34
Promoter
- Site where RNA polymerase & other transcription factors bind to DNA - TATA box, CAAT box, GC rich regions
35
Enhancer
Stretch of DNA that alters gene expression by binding transcription factors distant from START site
36
Silencer
Site where negative regulators bind
37
Pol I
rRNA
38
Pol II
mRNA
39
alpha-amanatin
- Found is death cap mushrooms - inhibits Pol II - Causes hepatotoxicity
40
Pol III
tRNA
41
Characteristics of RNA polymerase
- No proofreading function | - No primers
42
pre-mRNA or hnRNA
initial transcript that will become mature mRNA
43
RNA processing steps
1) Capping 5' end (methylguanosine) 2) Polyadenylation of 3' end 3) Splicing out introns - ALL occurs in the NUCLEUS
44
Introns vs. Exons
- Exons contain actual genetic information - Introns are intervening noncoding segments Think: - INtrons are INtervening sequences and stay IN the nucleus - EXons EXit the nucleus and are EXpressed
45
Aminoacyl-tRNA synthetase
- Charges tRNA | - Responsible for accuracy of amino acid selection
46
tRNA Wobble
- Accurate base pairing is only required in the first two nucleotide positions of an mRNA codon - Codons differing in 3rd "wobble" position may code for the same tRNA - Insoine
47
Translation Initiation
- GTP hydrolysis - eIFs (eukaryotic Initiation Factors) help assemble 40S ribosomal subunit (small) with initiator tRNA & are released when mRNA & 60S subunit (large) assemble the complex Think: - ATP= tRNA Activation - GTP= tRNA Gripping & Going places
48
Translation Elongation
1) Aminoacyl-tRNA binds to A-site (EXCEPT initiator methionine tRNA) 2) rRNA, "ribozyme" catalyzes peptide bond formation & transfers growing polypeptide to amino acid in A site 3) Ribosome advances 3 nucleotides, moving peptidyl tRNA to the P site Think: APE - A= incoming Aminoacyl-tRNA - P= accommodates growing Peptide - E= holds Empty tRNA as it Exits
49
Termination
- STOP codon recognized by release factor in A site | - Completed polypeptide is released from ribosome
50
Post-translational Modifications
- Trimming: Removal of N or C terminal propeptides | - Covalent Alterations: Phosphorylation, Glycosylation, Hydroxylation, Methylation, Acetylation, Ubiquitination
51
Chaperone Protein
- Intracellular protein involved in facilitating and/or maintaining folding - Heat Shock Proteins e.g. Hsp60
52
Cyclins
- Regulatory proteins that control cell cycle events - Phase specific - Activate CDKs
53
Rough Endoplasmic Reticulum
- Site of synthesis of secretory (exported) proteins | - Site of N-linked oligosaccharide addition to many proteins
54
Golgi Apparatus
- Distribution center for protein & lipids from the ER to vesicles & plasma membrane - Modifies N-oligosaccharides on asparagine - Adds O-oligosaccharides on serine & threonine - Adds mannose 6-phosphate to proteins for trafficking to lysosomes
55
I-cell Disease
- Inclusion Cell Disease - Inherited lysosomal storage disorder - Caused by defect in phosphotransferase (failure of Golgi to phosphorylate mannose)
56
SRP
- Signal Recognition Peptide | - Cytosolic Ribonucleoprotein that traffics proteins from the ribosome to the RER
57
Proteaseome
Barrel-shaped protein complex that degrades damaged or polyubiquitinated proteins

Biochemistry (17 decks)

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