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Module 1 Genetics > Translation > Flashcards

Translation Flashcards

1
Q

what does a redundant or degenerate genetic code mean?

A
  • Some amino acids must have more than one codon (64 possible amino acids, but only 20, so multiple codons code for an AA)
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2
Q

what kind of mutation is found in CF?

A
  • ΔF508 mutation of CF
    • deletion of phenylalanine at amino acid position 508
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3
Q

name the stop codons

A
  • yoU Are Away
  • yoU Go Away
  • yoU Are Gone
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4
Q

only 2 AA have one codons…which?

A

Methionine (Met) and Trytophan (Trp). Except in mitochondria, where Trp has 2 codons

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5
Q

describe the structure of a functional ribosome

A
  • 3 binding sites
    • A site holds the tRNA that carries the next aa to be added to the chain
    • P site holdes the tRNA that carries the growing polypeptide chain
    • E site is the exit site, where discharged tRNAs leave the ribosome
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6
Q

describe the structure of the prok ribosome and the euk ribosome

A
  • Prok: 2 subunits which = 70s
    • 50 s = peptidyl transferase activity
    • 30 s
  • Euk: 2 subunits which = 80s
    • 60 s
    • 40 s
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7
Q

describe the tRNA secondary structure

A
  • Resembles a cloverleaf
  • The anticodon recognizes 3 bases on the mRNA by base pairing
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8
Q

describe the tertiary structure of tRNA

A
  • 3’end where amino acid is attached to
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9
Q

explain the Wobble Hypothesis

A
  • Wobble position is the 3rd nucleotide on the codon (most right position)
    • Where you can have non-traditional base pairing because of the degenerate genetic code
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10
Q

how are AA attached to tRNA?

A
  • 2 step process
    • Enzyme bound amino-acid adenylate
    • Formation of the aminoacyl-tRNA (aka charged)
  • Reaction is driven by hydrolysis of pyrophosphate
  • tRNA attached to amino acid is called the “charged tRNA”
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11
Q

what is the first AA in prokes and mitochondria?

A
  • fMet-tRNA
  • This special tRNA is recognized differently by the ribosome–allows initiation
  • Prokes have 2tRNAs for methionine, one allows formation of fMet, the other recognizes internal AUG codons
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12
Q

what is the first AA in euks?

A
  • The first codon also uses Met, and it has a special tRNA for this first codon, but not formylated
  • Normal Met-tRNA for internal codons
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13
Q

describe the function of the Shine-Dalgarno sequence

A
  • Prokaryotes have a SD sequence which is purine rich and resides a few bases 5’ to the start codon
  • Euks don’t have a SD sequence, therefore euk small ribosome binds close to the cap at the 5’end, scans until it encounters the AUG start codon
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14
Q

describe the protein synthesis in translation

A
  1. Initiation factors (IFs) aid in the formation of the 30s initiation complex. The charged initiator tRNA is brought to the P site of the 30s subunit by IF-2-GTP
  2. GTP on IF-2 is hydrolyzed and initiation factors are released when the 50s subunit arrives to form the 70s initiation complex
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15
Q

describe the elongation process in protein synthesis

A
  1. Elongation factor EF-Tu-GTP brings the appropriate charged tRNA to the codon in the empty A site (decoding). GTP on EF-TU is hydrolyzed
  2. Peptidyltransferase, an activity of the 23S rRNA of the 50s subunit, catalyzes peptide bond formation, transferring the initiating AA (or peptide chain) from the P site to the amino acid at the A site (transpeptidation).

**Catalyzed by an enzymatic actvity of the RNA portion of the 50s ribosome – a Ribozyme

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16
Q

describe the next steps of elongation and termination

A
  1. EF-G-GTP facilitates movement of the ribosome 3 nucleotides along the mRNA in the 5’ to 3’ direction. What was in the P site is now in the E, A now in P, and A is empty.
  2. Steps 3, 4, 5 repeated until termination codon in A site.
  3. A termination codon is recognized by a release factor (RF-1 or RF-2) which results in release of the newly synthesized protein. GTP on RF-3 is hydrolyzed. The complex dissociates
17
Q

describe the process of protein folding

A
  • Occurs during translation
  • Spontaneous or facilitated by chaperones
18
Q

differences between prok and euk translation

A
  • Euk
    • first MET is not formylated
    • monocistronic
    • typically start translation at first AUG site
    • may not couple bc of nucleaer membrane
  • Prok
    • first MET is formylated (fMET)
    • polycistronic
    • may select an internal AUG to start translation
    • translation and transcription are coupled
19
Q

describe the function of diphtheria toxin

A
  • Inactivation of EF-2 (euks) by adding ADP-ribose to it
20
Q

describe the function of stretomycin

A
  • Prevents assembly of ribosome (binds to 30s subunit)
  • Inhibits initiation
21
Q

describe the function of tetracyclin

A
  • Four (tetra) ring (cyclic) structure
  • Blocks elongation by preventing aminoacyl-tRNA access to the A-site
22
Q

describe the function of erythromycin (macrolide)

A
  • Binds to the 50s subunit of the ribosome
  • Blocks ribosome translocation
  • macroSLIDES –> blocks translocation
23
Q

chloramphenicol

A
  • inhibits peptidyl transferase activity in proks
  • at high levels, may inhibit mitochondrial translation
24
Q

describe the function of cycloheximide

A
  • inhibits euk peptidyl transferase activity
  • Used for research in labs
25
Q

describe the function of puromycin

A
  • causes premature termination of translation in both proks and euks
26
Q

describe zymogen activation

A
  • Zymogen (or proenzyme): an inactive enzyme precursor
    • activated within an organism into active enzymes
    • activation by enzymatic cleavage of peptide bonds of the zymogen molecules
  • Cascade of zymogen activation:
    • caspases to activate apoptosis
    • blood coagulation
    • digestion of proteins
27
Q

what is the purpose of protein phosphorylation

A
  • Serine/Threonine
    • phosphate is transferred from ATP to a protein on a Ser/Thr residue of a protein
    • More common than tyr phosphorylation
  • Tyrosine
    • phosphate is transferred from ATP to a protein on a Tyr reside of a protein
    • the insulin receptor is a tyrosine kinase
28
Q

explain the process of glycosylation

A
  • may occur as either one type of linkage or with both on the same protein
29
Q

describe the process of lipid anchoring

A
  • Lipid anchoring
    • have proteins that need to interact with the lipids in the PM; need to add Farnesyl which lets it interact with the lipid bilayer
  • The cell targets Ras to the PM by a lipid anchor mechanism
30
Q

describe proteolytic processing of insulin

A
  • Insulin and its C-peptide are packaged together into secretory vesicles to be made ready for secretion
  • C-peptide is essential for proper insulin folding
  • C-peptide is a good indicator of insulin production and secretion because its (C-peptide) half-life in the plasma is longer than that of insulin

Module 1 Genetics (21 decks)

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