Question 1

Which of the following best describes the role of the Shine-Dalgarno sequence in bacterial translation initiation?

Accepted Answer

It aligns the ribosome with the correct start site on mRNA by pairing with the 16S rRNA.

Question 2

A mutation changes the DNA coding strand from 5'-ATGGGCT-3' to 5'-ATGAGCT-3'. What is the effect on the resulting polypeptide sequence?

Accepted Answer

There will be a missense mutation, substituting one amino acid for another.

Question 3

Which statement about the genetic code is correct?

Accepted Answer

The genetic code is universal and unambiguous, with each codon specifying only one amino acid.

Question 4

During translation, which ribosomal site is responsible for holding the tRNA carrying the growing polypeptide chain?

Accepted Answer

P (peptidyl) site

Question 5

A patient with sickle cell anemia has a single amino acid substitution in hemoglobin. Which molecular event most likely caused this?

Accepted Answer

A missense mutation resulting in a single nucleotide change.

Question 6

What is the function of aminoacyl-tRNA synthetases in translation?

Accepted Answer

They attach the correct amino acid to its corresponding tRNA.

Question 7

Which of the following codons acts as a start codon in eukaryotic and prokaryotic translation?

Accepted Answer

$$	ext{AUG}$$

Question 8

If the template DNA strand is 3'-TACCCGA-5', what is the corresponding mRNA sequence?

Accepted Answer

$$5'-AUGGGCU-3'$$

Question 9

Which process is facilitated by molecular chaperones such as Hsp70 and Hsp60?

Accepted Answer

Folding of newly synthesized polypeptides into their functional shapes

Question 10

A tRNA with the anticodon 3'-GCI-5' can pair with which mRNA codons due to wobble base pairing?

Accepted Answer

$$5'-GCU-3'$$, $$5'-GCC-3'$$, and $$5'-GCA-3'$$

Question 11

Which of the following best explains why multiple ribosomes can translate a single mRNA molecule simultaneously?

Accepted Answer

Multiple ribosomes can attach to the same mRNA, forming a polyribosome and increasing translation efficiency.

Question 12

Which event occurs during the elongation phase of translation?

Accepted Answer

Aminoacyl-tRNA enters the A site and a peptide bond forms between amino acids.

Question 13

What is the consequence of a nonsense mutation in a coding region of a gene?

Accepted Answer

It introduces a premature stop codon, truncating the protein.

Question 14

Which of the following is NOT a function of translation initiation factors?

Accepted Answer

Catalyzing peptide bond formation between amino acids

Question 15

Which of the following best describes the process of translation termination?

Accepted Answer

A release factor recognizes a stop codon and promotes the release of the polypeptide from the ribosome.

Question 16

Which of the following statements about the directionality of translation is correct?

Accepted Answer

Translation begins at the N-terminus and proceeds to the C-terminus, reading mRNA 5' to 3'.

Question 17

Which of the following is a property of the genetic code that allows for 'wobble' base pairing?

Accepted Answer

The third base of the codon can pair non-standardly with the anticodon.

Question 18

Which of the following is true regarding stop codons?

Accepted Answer

They signal the end of translation and are recognized by release factors.

Question 19

A researcher isolates a mutant tRNA that cannot be charged with its amino acid. What is the most likely consequence for protein synthesis?

Accepted Answer

The ribosome will stall at the codon corresponding to the mutant tRNA, leading to incomplete polypeptides.

Gene Expression II: Protein Synthesis and Sorting (Chapter 19) – Study Notes

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