Question 1

Which of the following statements correctly describes the role of the start codon in translation initiation in eukaryotes?

Accepted Answer

The start codon AUG is recognized by the initiator tRNA, which carries methionine and directly enters the P site of the small ribosomal subunit.

Question 2

During translation, which of the following best describes the directionality of polypeptide synthesis?

Accepted Answer

Polypeptides are synthesized from the N terminus to the C terminus.

Question 3

Which equation correctly represents the formation of a peptide bond between two amino acids?

Accepted Answer

$$\mathrm{NH_2${-}$$CHR_1$${-}COOH} + \mathrm{NH_2${-}$$CHR_2$${-}COOH} \rightarrow \mathrm{NH_2${-}$$CHR_1$${-}CO{-}NH{-}$$CHR_2$${-}COOH} + H_2O$$

Question 4

A mutation changes the codon AUG to UAG in the middle of an mRNA sequence. What is the most likely consequence for the resulting protein?

Accepted Answer

Translation will terminate prematurely at the UAG codon, resulting in a truncated protein.

Question 5

Which of the following best explains why the Svedberg unit (S) used to describe ribosomal subunits is not directly additive?

Accepted Answer

The Svedberg unit reflects sedimentation rate, which depends on size, shape, and density, not just mass.

Question 6

In prokaryotes, what sequence is recognized by the ribosome to initiate translation?

Accepted Answer

The Shine-Dalgarno sequence

Question 7

Which of the following statements about tRNA charging is correct?

Accepted Answer

Aminoacyl-tRNA synthetases specifically attach the correct amino acid to its corresponding tRNA, and there are 20 such enzymes.

Question 8

Which of the following best describes the function of EF-Tu in prokaryotic translation elongation?

Accepted Answer

EF-Tu delivers aminoacyl-tRNA to the A site of the ribosome in its GTP-bound form and is released upon GTP hydrolysis.

Question 9

Which of the following is true regarding the polarity of polypeptides?

Accepted Answer

Polypeptides have polarity, with the N terminus (amino end) synthesized first and the C terminus (carboxyl end) synthesized last.

Question 10

Which of the following best describes the role of the ribosome during translation?

Accepted Answer

The ribosome catalyzes the formation of peptide bonds and ensures correct base pairing between codon and anticodon.

Question 11

A researcher treats cells with puromycin. What is the most likely effect on translation?

Accepted Answer

Puromycin mimics aminoacyl-tRNA, accepts the growing peptide chain, and causes premature chain termination.

Question 12

Which of the following is a key difference between translation initiation in prokaryotes and eukaryotes?

Accepted Answer

Prokaryotes use the Shine-Dalgarno sequence upstream of the start codon, while eukaryotes rely on the Kozak consensus sequence surrounding AUG.

Question 13

Which of the following equations represents the hydrolysis of GTP during translation elongation?

Accepted Answer

$$\mathrm{GTP} + H_2O ightarrow \mathrm{GDP} + P_i + 	ext{energy}$$

Question 14

Which of the following statements about ribosomal subunits is correct?

Accepted Answer

The large subunit contains the peptidyl transferase center and catalyzes peptide bond formation.

Question 15

During translation elongation, what is the correct order of tRNA movement through the ribosome?

Accepted Answer

A site → P site → E site

Question 16

Which of the following best explains why translation proceeds in an orderly manner?

Accepted Answer

Elongation factors such as EF-Tu and EF-G use GTP hydrolysis to regulate the entry and release of tRNAs and ensure proper translocation.

Question 17

A patient is diagnosed with a genetic disorder caused by a mutation in an aminoacyl-tRNA synthetase gene. Which of the following is the most likely molecular consequence?

Accepted Answer

Incorrect amino acids will be incorporated into proteins, potentially leading to dysfunctional proteins.

Question 18

Which of the following is true about polycistronic mRNAs?

Accepted Answer

They are found in prokaryotes and can encode multiple proteins from a single mRNA by having multiple translation start sites.

Translation: The Genetic Code and Protein Synthesis

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