9. Proteins And Their Synthesis Flashcards

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1
Q

Prokaryotic vs. eukaryotic transcription and translation

A

Prokaryotes:
RNA not processed
Translation on site

Eukaryotes:
RNA processed
Translation following RNA transport

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2
Q

Ribosomes

A

Decoding hubs

Prokaryotes:
Small subunit: 30S
Large subunit: 50s

Eukaryotes
Small subunit: 40S
Large subunit: 60S

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3
Q

RRNA

A

Folds up by intramolecular base pairing

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4
Q

TRNA

A

Transfer RNAs
Small adapters between amino acids and codons in mRNA molecules

Anticodon of tRNA base pairs with codon of mRNA

Amino acid covalently attached to 3’ end of tRNA

Often contain modified nucleosides

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5
Q

Aminacyl-tRNA synthetase

A

Attaches an amino acid to its specific tRNA

Codon specifies resides in tRNA, NOT attached to amino acid

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6
Q

Ribosomal domains

A

APE
Aminoacyl binding site
Peptides binding site
Exit binding site

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7
Q

Steps of translation

A

1) polypeptide chain initiation
2) chain elongation (peptide bonds)
3) chain termination

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8
Q

Shine-dalagarno sequence

A

MRNA and ribosomal recognition in prokaryotes; aligns at p-site

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9
Q

Prokaryotes initiation factors

A

IF 1
IF 2
IF 3

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10
Q

Translation initiation in prokaryotes

A

Initiation factor

1st ATG recognized and bound to MET at P site

MET tRNA associates to 40S subunit

40S scans for 1st AUG and binds

Initiator factors leave

Large subunit assembles AUG positioned at P-site

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11
Q

Termination: release factors

A

Prokaryotes:
RF 1, 2, 3

Eukaryotes:
ERF

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12
Q

Initiation stage (steps)

A

Binding of MET-tRNA to mRNA and small subunit of ribosome

Large subunit combines with small subunit

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13
Q

Elongation stage (steps)

A

Incoming aminoacyl tRNA fits into A-site

Bond formed between methionine and amino acid molecule on tRNA

Repeated until amino acid chain is formed

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14
Q

Termination stage (steps)

A

Ribosomes reaches stop codon

Amino acid chain detaches from ribosome

TRNA and ribosomal subunits dissociate from mRNA

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15
Q

How is frame established?

A

1st ATG (MET) in the mRNA establishes frame

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16
Q

Synthetic mRNA molecules

A

Used to deduce codon sequence

E.g., poly uracil mRNA encodes a poly phe peptide

17
Q

Properties of genetic code

A
  1. Composed of nucleotide triplets
  2. Non overlapping
  3. Commafree
  4. Degenerate
  5. Contains start and stop codons
  6. Nearly universal
18
Q

Mutations in tRNA genes

A

Specificity and degeneracy of genetic code can be affected by mutations

19
Q

Wobble rules

A

Codon-anticodon pairings at 3rd base allows for wobble rules

20
Q

Codon-anticodon pairings

A
G—>C or U
C—>G
A—>U
U—>A or G
I—> U, C, or A
21
Q

Mutations in tRNA genes change anticodon specifity can reengineer the genetic code in cells

A

Shorter, mutant transcript

Premature termination

22
Q

Amber (UAG) mutation

A

Nonsense mutation that changes sense codon into translational stop codon (UAG)

Causes premature termination in translation

23
Q

Suppressor tRNA & amber mutation

A

Suppresses amber mutation and results in wild type phenotype

Counteracts the effects of a nonsense mutation