Question 1

Which of the following statements best describes the function of the Shine-Dalgarno sequence in bacterial translation?

Accepted Answer

It serves as a binding site for ribosomes to initiate translation.

Question 2

What is the consequence of a frameshift mutation caused by the insertion of a single nucleotide in a coding region?

Accepted Answer

All codons downstream of the mutation are read incorrectly, potentially altering the entire protein sequence.

Question 3

Which of the following codons is universally recognized as the start codon in translation?

Accepted Answer

AUG

Question 4

In the context of polyribosomes, what is the main advantage of having multiple ribosomes translating a single mRNA molecule simultaneously?

Accepted Answer

It allows for rapid and efficient production of multiple copies of the same polypeptide.

Question 5

Which release factor in bacteria recognizes both UAA and UGA stop codons?

Accepted Answer

RF2

Question 6

A mutation changes the DNA sequence from $$	ext{TAC} to$$ $$	ext{TAT}. $$What is the effect on the mRNA codon and the resulting amino acid, given the genetic code's redundancy?

Accepted Answer

The mRNA codon changes, but the amino acid may remain the same due to synonymous codons.

Question 7

Which of the following best explains the concept of third-base wobble in tRNA-codon pairing?

Accepted Answer

Flexible pairing at the third base of the codon allows one tRNA to recognize multiple codons.

Question 8

Which of the following is a direct result of posttranslational processing in proteins?

Accepted Answer

Cleavage of N-terminal amino acids such as methionine or fMet.

Question 9

If a synthetic mRNA composed entirely of $$	ext{UUU}$$ codons is translated in vitro, which amino acid will be incorporated into the polypeptide?

Accepted Answer

Phenylalanine

Question 10

Which of the following statements about polycistronic mRNA is correct?

Accepted Answer

It contains multiple genes, each with its own start and stop codon.

Question 11

A protein is found to be inactive until a phosphate group is added to a specific amino acid. Which enzyme is responsible for this activation?

Accepted Answer

Kinase

Question 12

Which of the following is NOT a stop codon?

Accepted Answer

AUG

Question 13

What is the effect of a reversion mutation that deletes a nucleotide near a previous insertion mutation in a gene?

Accepted Answer

It restores the original reading frame, normalizing the protein sequence downstream.

Question 14

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

Accepted Answer

They bind to stop codons in the A site and trigger release of the polypeptide from the ribosome.

Question 15

Which of the following amino acids is specified by only one codon in the genetic code?

Accepted Answer

Methionine

Question 16

A scientist observes that a protein is produced as a precursor and then cleaved to form two separate functional chains. Which hormone is an example of this process?

Accepted Answer

Insulin

Question 17

Which of the following is a consequence of codon usage bias in an organism?

Accepted Answer

It can affect the rate of translation elongation and gene expression efficiency.

Question 18

Which experimental evidence disproved the hypothesis of an overlapping genetic code?

Accepted Answer

Single nucleotide changes resulted in single amino acid changes.

Question 19

During translation at the endoplasmic reticulum, what is the role of the signal sequence in a newly synthesized polypeptide?

Accepted Answer

It directs the ribosome to the ER membrane for co-translational import.

Question 20

If a bacterial cell has only 40 different tRNAs but 61 codons specify amino acids, which mechanism allows this discrepancy?

Accepted Answer

Third-base wobble allows some tRNAs to recognize multiple codons.

Translation: Mechanisms, Genetic Code, and Posttranslational Processing

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