Question 1

Which of the following statements best describes the degeneracy of the genetic code?

Accepted Answer

Multiple codons can specify the same amino acid, allowing for redundancy in the code.

Question 2

A mutation changes the third base of a codon from C to U, but the amino acid sequence of the protein remains unchanged. Which property of the genetic code explains this phenomenon?

Accepted Answer

Degeneracy (wobble position)

Question 3

During translation in bacteria, which sequence on the mRNA helps the ribosome identify the correct start codon?

Accepted Answer

Shine-Dalgarno sequence

Question 4

Which of the following best describes the function of aminoacyl-tRNA synthetase?

Accepted Answer

It attaches the correct amino acid to its corresponding tRNA.

Question 5

A scientist discovers a new organism in which the codon UGA codes for tryptophan instead of acting as a stop codon. What does this observation illustrate?

Accepted Answer

There are exceptions to the universality of the genetic code.

Question 6

Which of the following correctly matches the ribosomal sites with their primary function during translation elongation?

Accepted Answer

A site: tRNA entry; P site: peptide bond formation; E site: tRNA exit

Question 7

In eukaryotic translation initiation, which of the following features is essential for efficient ribosome binding and scanning?

Accepted Answer

5' methylguanosine cap and poly-A tail

Question 8

Which of the following best explains why fewer than 61 tRNAs are required to recognize all sense codons?

Accepted Answer

The presence of modified bases in tRNA allows for wobble pairing at the third codon position.

Question 9

A patient is diagnosed with a neurodegenerative disease caused by the accumulation of misfolded proteins forming amyloid plaques. Which molecular process is most directly implicated in this pathology?

Accepted Answer

Protein misfolding and aggregation

Question 10

Which of the following post-translational modifications is most likely to alter the function of a protein by adding a phosphate group to specific amino acids?

Accepted Answer

Phosphorylation

Question 11

A mutation in the gene encoding a chaperone protein leads to increased aggregation of newly synthesized polypeptides. What is the most likely cellular consequence?

Accepted Answer

Increased risk of protein misfolding diseases

Question 12

Which of the following equations correctly represents the number of possible codons in the genetic code, given that there are four different nucleotides and codons are three nucleotides long?

Accepted Answer

$$4^3 = 64$

Question 13

In prokaryotes, what is the role of the Shine-Dalgarno sequence during translation initiation?

Accepted Answer

It aligns the ribosome with the start codon on the mRNA.

Question 14

Which of the following best describes the process of tRNA charging?

Accepted Answer

Aminoacyl-tRNA synthetase attaches an amino acid to its corresponding tRNA using ATP.

Question 15

A researcher observes that a certain tRNA can pair with three different codons for the same amino acid. Which molecular feature allows this flexibility?

Accepted Answer

The presence of inosine at the wobble position of the tRNA anticodon

Question 16

Which of the following is a key difference between prokaryotic and eukaryotic translation?

Accepted Answer

Eukaryotic ribosomes are larger and require more initiation factors than prokaryotic ribosomes.

Question 17

A mutation eliminates the function of release factors in a bacterial cell. What is the most likely effect on protein synthesis?

Accepted Answer

Polypeptide chains will not be released from the ribosome at stop codons.

Question 18

Which of the following best explains why overlapping open reading frames (ORFs) are rare in eukaryotic genomes but more common in some viruses?

Accepted Answer

Viruses maximize coding capacity in small genomes by using overlapping ORFs.

Question 19

Which of the following best describes the function of chaperone proteins in the cell?

Accepted Answer

They assist in the proper folding of newly synthesized polypeptides and prevent aggregation.

Lecture 11 and 12 (ch13&14)

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