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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

What does translation result in?

Protein synthesis

Where does translation occur?

In the ribosome

What does the ribosome contain?

rRNA and many other proteins

In translation, what carries amino acids to the ribosome and binds to its complement in the mRNA template?

tRNA

What dictates amino acids?

Genetic code

Why is the genetic code degenerate?

Several mRNA codons may correspond to the same amino acid

What can bind to more than one of the codons that specify their amino acid?

tRNAs

What is the Wobble hypothesis?

The third codon position and the 5' anticodon position experience some flexibility

What is inosine (I)?

A deaminated form form of adenosine and is found in the anticodon sequence in tRNAs

What does the Wobble hypothesis explain?

Why many codons can be bound with fewer tRNAs

How many nucleotides does a tRNA contain?

76

What shape is tRNA in 3D?

L-shaped

How do amino acids attach to tRNA?

Via aminoacylation at the 3'-OH

What occurs during the aminoacyl-tRNA synthase reaction?

Addition of amino acid to tRNA is catalyzed by aminoacyl-tRNA synthetase



What is required for the aminoacyl-tRNA synthase reaction?

ATP

How many types of aminoacyl-tRNA synthetases are there?

20

Extensive interactions form between what two things in aminoacyl-tRNA synthesase reaction?

tRNAs and their respective aminoacyl-tRNA synthetases

tRNA anticodons pair with what in aminoacyl-tRNA synthase reactions?

mRNA codons

What is the ribosome composed of?

rRNA and many proteins

What is a ribosome?

rRNA and proteins complex that synthesizes protein

What does the conformation of rRNA determine?

The structure of a ribosome

How many tRNAs can bind to a ribosome at one time?

Three

What is required for the initiation of translation?

An initiator tRNA

What is the genetic code for the start codon in the initiation state of translation?

AUG

Where is the methionine in the initiator tRNA derived from?

An N-formyl group

In prokaryotic mRNAs, where is the initiation codon located?

10 bases downstream of the Shine-Dalgarno sequence

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

What are the two characteristics of eukaryotic initiation of translation?

1. It is circular


2. Involves at least 12 initiation factors

What do aminoacyl-tRNAs bind to?

EF-Tu with approximately the same affinity

What is EF-Tu?

A prokaryotic elongation factor

What is an aminoacyl-tRNA delivered to the ribosome in complex with?

An elongation factor

What does EF-Tu ensure?

That polymerization does not occur unless the correct aminoacyl-tRNA is positioned in the A-site

What does EF-G facilitate?

Translocation of mRNA and tRNA

What do release factors mediate?

Translation termination

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

T or F: Translation is efficient in vivo

True

What is the first chaperone that a bacterial protein meets?

The trigger factor

What are chaperons?

Proteins that facilitate protein folding

What promotes protein folding after translation?

Molecular chaperones

What are chaperonins?

Complexes of molecular chaperones that physically sequester a folding polypeptide

T or F: Many proteins do not undergo covalent modification

False

What is the conversion of proinsulin to unsulin involves proteolysis an example ofM

A protein undergoing covalent modification