Question 1

Which of the following statements best describes the directionality of protein synthesis during translation?

Accepted Answer

Proteins are synthesized from the N-terminus to the C-terminus.

Question 2

A mutation changes the codon GAA (which codes for Glu) to UAA in an mRNA sequence. What is the most likely effect of this mutation on the resulting protein?

Accepted Answer

The protein will be truncated due to the introduction of a stop codon.

Question 3

Which of the following best explains why the genetic code is described as 'degenerate'?

Accepted Answer

Some amino acids are specified by more than one codon.

Question 4

During translation, which molecule carries the amino acid to the ribosome and recognizes the codon on the mRNA?

Accepted Answer

tRNA

Question 5

A tRNA has the anticodon 5'-UAC-3'. Which mRNA codon will it recognize and bind to during translation?

Accepted Answer

5'-AUG-3'

Question 6

Which of the following is the correct sequence of events during the elongation phase of translation?

Accepted Answer

Binding of aminoacyl-tRNA to the A site, peptide bond formation, translocation

Question 7

Which of the following antibiotics inhibits protein synthesis by binding to the 50S ribosomal subunit and blocking peptidyl transferase activity?

Accepted Answer

Chloramphenicol

Question 8

A patient is diagnosed with a lysosomal storage disease due to a defect in protein targeting. Which cellular process is most likely impaired?

Accepted Answer

Transport of proteins to the lysosome via the mannose-6-phosphate pathway

Question 9

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

Accepted Answer

It attaches the correct amino acid to its corresponding tRNA using ATP.

Question 10

A frameshift mutation is most likely to result from which of the following types of DNA changes?

Accepted Answer

Insertion or deletion of one or two nucleotides

Question 11

Which of the following codons is a stop codon in the genetic code?

Accepted Answer

$$\mathrm{UAA}$$

Question 12

If the mRNA sequence is 5'-AUG-GCC-UUU-GGA-UAA-3', what is the corresponding amino acid sequence?

Accepted Answer

Met-Ala-Phe-Gly

Question 13

Which of the following posttranslational modifications is most likely to target a protein for degradation by the proteasome?

Accepted Answer

Ubiquitination

Question 14

A mutation in the gene encoding the signal recognition particle (SRP) would most directly affect which process?

Accepted Answer

Targeting of proteins to the rough endoplasmic reticulum

Question 15

Which of the following best explains why only one tRNA synthetase exists for each amino acid, despite the degeneracy of the genetic code?

Accepted Answer

Each tRNA synthetase recognizes all tRNAs for a given amino acid.

Question 16

Which of the following events occurs during the termination phase of translation?

Accepted Answer

A release factor binds to the stop codon in the A site.

Question 17

A patient is treated with an antibiotic that prevents the binding of aminoacyl-tRNA to the A site of the ribosome. Which antibiotic is most likely responsible for this effect?

Accepted Answer

Tetracycline

Question 18

Which of the following best describes the 'wobble' hypothesis in tRNA-codon pairing?

Accepted Answer

The third base of the codon can pair with multiple bases in the anticodon.

Question 19

Which of the following is a real-life consequence of a frameshift mutation in a gene encoding a lysosomal enzyme?

Accepted Answer

The enzyme is truncated and nonfunctional, leading to substrate accumulation in lysosomes.

Question 20

Which of the following steps in translation requires GTP hydrolysis?

Accepted Answer

Binding of aminoacyl-tRNA to the A site

Translation: Synthesis of Proteins – Genetic Code, Mechanism, and Regulation

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