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43 Cards in this Set
- Front
- Back
What is the genetic code based on? |
3-nucleotide codons that are read in sequential and nonoverlapping order |
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What does translation result in? |
Protein synthesis |
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Where does translation occur? |
In the ribosome |
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What does the ribosome contain? |
rRNA and many other proteins |
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In translation, what carries amino acids to the ribosome and binds to its complement in the mRNA template? |
tRNA |
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What dictates amino acids? |
Genetic code |
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Why is the genetic code degenerate? |
Several mRNA codons may correspond to the same amino acid |
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What can bind to more than one of the codons that specify their amino acid? |
tRNAs |
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What is the Wobble hypothesis? |
The third codon position and the 5' anticodon position experience some flexibility |
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What is inosine (I)? |
A deaminated form form of adenosine and is found in the anticodon sequence in tRNAs |
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What does the Wobble hypothesis explain? |
Why many codons can be bound with fewer tRNAs |
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How many nucleotides does a tRNA contain? |
76 |
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What shape is tRNA in 3D? |
L-shaped |
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How do amino acids attach to tRNA? |
Via aminoacylation at the 3'-OH |
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What occurs during the aminoacyl-tRNA synthase reaction? |
Addition of amino acid to tRNA is catalyzed by aminoacyl-tRNA synthetase |
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What is required for the aminoacyl-tRNA synthase reaction? |
ATP |
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How many types of aminoacyl-tRNA synthetases are there? |
20 |
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Extensive interactions form between what two things in aminoacyl-tRNA synthesase reaction? |
tRNAs and their respective aminoacyl-tRNA synthetases |
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tRNA anticodons pair with what in aminoacyl-tRNA synthase reactions? |
mRNA codons |
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What is the ribosome composed of? |
rRNA and many proteins |
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What is a ribosome? |
rRNA and proteins complex that synthesizes protein |
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What does the conformation of rRNA determine? |
The structure of a ribosome |
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How many tRNAs can bind to a ribosome at one time? |
Three |
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What is required for the initiation of translation? |
An initiator tRNA |
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What is the genetic code for the start codon in the initiation state of translation? |
AUG |
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Where is the methionine in the initiator tRNA derived from? |
An N-formyl group |
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In prokaryotic mRNAs, where is the initiation codon located? |
10 bases downstream of the Shine-Dalgarno sequence |
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Summarize translation initiation in prokaryotes (2 steps): |
1. mRNA and fMet-tRNA in complex with IF-2-GTP bind to the small (30S) ribosomal subunit 2. Association of the large (50S) subunit with the 30S subunit triggers IF-2 to hydrolyze its bound GTP |
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What are the two characteristics of eukaryotic initiation of translation? |
1. It is circular 2. Involves at least 12 initiation factors |
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What do aminoacyl-tRNAs bind to? |
EF-Tu with approximately the same affinity |
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What is EF-Tu? |
A prokaryotic elongation factor |
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What is an aminoacyl-tRNA delivered to the ribosome in complex with? |
An elongation factor |
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What does EF-Tu ensure? |
That polymerization does not occur unless the correct aminoacyl-tRNA is positioned in the A-site |
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What does EF-G facilitate? |
Translocation of mRNA and tRNA |
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What do release factors mediate? |
Translation termination |
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What are the three steps in translation termination in E.coli? |
1. A release factor (RF-1 or RF-2) recognizes a stop codon in the A site 2. RF-1/RF-2 causes the ribosome to transfer the peptidyl group to water to release the polypeptide chain 3. GTP hydrolysis by RF-3 allows the release factors to dissociate. Additional steps are required to prepare the ribosome for another round of translation |
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T or F: Translation is efficient in vivo |
True |
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What is the first chaperone that a bacterial protein meets? |
The trigger factor |
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What are chaperons? |
Proteins that facilitate protein folding |
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What promotes protein folding after translation? |
Molecular chaperones |
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What are chaperonins? |
Complexes of molecular chaperones that physically sequester a folding polypeptide |
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T or F: Many proteins do not undergo covalent modification |
False |
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What is the conversion of proinsulin to unsulin involves proteolysis an example ofM |
A protein undergoing covalent modification |