Q: Which of the following equations correctly represents the reaction catalyzed by aminoacyl-tRNA synthetase?

$$\text{Amino acid} + \text{tRNA} + \text{ATP} \xrightarrow{\text{aminoacyl-tRNA synthetase}} \text{aminoacyl-tRNA} + \text{AMP} + \text{PP}_i$$

Question 1

Which of the following statements best describes the role of aminoacyl-tRNA synthetases in translation?

Accepted Answer

They covalently link specific amino acids to their corresponding tRNAs using ATP hydrolysis.

Question 2

During translation in bacteria, what is the function of the Shine-Dalgarno sequence?

Accepted Answer

It aligns the mRNA on the small ribosomal subunit by base pairing with the 16S rRNA.

Question 3

Which ribosomal site is responsible for binding the tRNA carrying the growing polypeptide chain during elongation?

Accepted Answer

P (peptidyl) site

Question 4

A mutation changes the anticodon of a tRNA from 3'-UAI-5' to 3'-UAA-5'. Which codons can this mutated tRNA recognize according to the wobble hypothesis?

Accepted Answer

UAA only

Question 5

Which of the following best explains why fewer tRNAs are required than the number of codons for some amino acids?

Accepted Answer

Some tRNAs are able to recognize multiple codons due to wobble base pairing at the third codon position.

Question 6

In eukaryotic translation initiation, which sequence is most commonly involved in start site recognition?

Accepted Answer

Kozak sequence

Question 7

Which of the following is TRUE regarding the catalytic activity of peptide bond formation in the ribosome?

Accepted Answer

It is catalyzed by the 23S rRNA, making the ribosome a ribozyme.

Question 8

A researcher observes that a bacterial mRNA encodes three different polypeptides, each with related functions. What is the best explanation for this observation?

Accepted Answer

The mRNA is polycistronic and is part of an operon.

Question 9

Which of the following events occurs during the translocation step of elongation in translation?

Accepted Answer

The peptidyl tRNA moves from the A site to the P site, and the empty tRNA moves to the E site.

Question 10

Which of the following is a direct consequence of the hydrolysis of GTP by EF-G during translation elongation?

Accepted Answer

Translocation of the ribosome along the mRNA by three nucleotides.

Question 11

A patient is treated with an antibiotic that specifically inhibits the 70S ribosome. Which type of cell would be most affected?

Accepted Answer

Bacterial cells

Question 12

Which of the following best describes the role of release factors in translation termination?

Accepted Answer

They bind to the stop codon at the A site and trigger release of the polypeptide from the ribosome.

Question 13

Which of the following is a feature unique to eukaryotic mRNAs that enhances translation initiation?

Accepted Answer

5' cap structure and poly(A) tail

Question 14

Which of the following equations correctly represents the reaction catalyzed by aminoacyl-tRNA synthetase?

Accepted Answer

$$	ext{Amino acid} + 	ext{tRNA} + 	ext{ATP} \xrightarrow{	ext{aminoacyl-tRNA synthetase}} 	ext{aminoacyl-tRNA} + 	ext{AMP} + 	ext{PP}_i$$

Question 15

Which of the following statements about polyribosomes (polysomes) is correct?

Accepted Answer

They are clusters of ribosomes translating the same mRNA molecule simultaneously.

Question 16

Which of the following is a consequence of the molecular mimicry between release factors and tRNAs?

Accepted Answer

Release factors can bind to stop codons at the A site and terminate translation.

Question 17

Which of the following best explains why the error rate in translation is at most 1/10,000?

Accepted Answer

Elongation factors only allow tRNAs with correct anticodon-codon pairing to remain at the A site long enough for GTP hydrolysis.

Question 18

Which of the following is TRUE regarding the directionality of mRNA translation?

Accepted Answer

mRNA is read in the 5' to 3' direction, and polypeptide synthesis begins at the N-terminus.

Gene Expression II: The Genetic Code and Protein Synthesis (Translation)

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