Question 1

Which of the following statements best describes the 'wobble hypothesis' as it relates to the genetic code?

Accepted Answer

It states that the third base of the codon and the first base of the anticodon can form non-standard base pairs, allowing one tRNA to recognize multiple codons.

Question 2

A mutation deletes the sixth nucleotide (a C) from the following mRNA sequence: 5'-AUG CCC GGA GGC ACC GUC CAA U-3'. What is the resulting effect on the encoded polypeptide?

Accepted Answer

A frameshift occurs, altering all downstream amino acids and likely producing a nonfunctional protein.

Question 3

Which of the following is TRUE regarding the initiation of translation in eukaryotes?

Accepted Answer

The 7-methylguanosine cap is recognized by initiation factors, and the ribosome scans for the start codon within a Kozak sequence.

Question 4

Which enzyme is responsible for attaching the correct amino acid to its corresponding tRNA, and what is the error rate of this process?

Accepted Answer

Aminoacyl-tRNA synthetase; error rate less than one in every 10,000

Question 5

A patient is treated with an antibiotic that binds to the 23S rRNA and blocks elongation by interfering with translocation. Which antibiotic is this, and why does it not harm human cells?

Accepted Answer

Erythromycin; because it specifically targets bacterial ribosomes, which differ from eukaryotic ribosomes

Question 6

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

Accepted Answer

Multiple codons can specify the same amino acid.

Question 7

During translation elongation in bacteria, which ribosomal RNA acts as the peptidyl transferase to catalyze peptide bond formation?

Accepted Answer

23S rRNA

Question 8

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

Accepted Answer

Bacteria use fMet-tRNA as the initiator, while eukaryotes use Met-tRNA.

Question 9

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

Accepted Answer

It base-pairs with the 16S rRNA to position the ribosome at the correct start codon.

Question 10

A synthetic RNA copolymer with the repeating sequence UC (UCUCUCUC...) is translated in a cell-free system. Which amino acids are incorporated into the resulting polypeptide?

Accepted Answer

Serine and leucine

Question 11

Which of the following is NOT a function of proteins as described in the study materials?

Accepted Answer

Storage of genetic information

Question 12

Which of the following statements about translation termination is CORRECT?

Accepted Answer

In bacteria, RF1 recognizes UAA and UAG, while RF2 recognizes UAA and UGA.

Question 13

Which of the following best explains why translation and transcription are coupled in bacteria but not in eukaryotes?

Accepted Answer

Bacteria lack a nucleus, so both processes occur in the cytoplasm.

Question 14

A mutation in a eukaryotic cell causes the loss of a guanine at the +4 position of the Kozak sequence. What is the most likely effect on translation?

Accepted Answer

The ribosome will fail to recognize the start codon efficiently, reducing translation initiation.

Question 15

Which of the following is a direct result of the degeneracy of the genetic code?

Accepted Answer

A single tRNA can recognize multiple codons due to wobble base pairing.

Question 16

Which of the following best describes the directionality of polypeptide synthesis during translation?

Accepted Answer

Amino acids are added to the carboxyl terminus, and the polypeptide grows from N-terminus to C-terminus.

Question 17

Which of the following is a real-world consequence of altered expression of eukaryotic translation initiation factors (eIFs)?

Accepted Answer

Increased eIF expression can promote tumorigenesis and resistance to anticancer drugs.

Question 18

Which of the following best describes the experimental approach used by Nirenberg and Leder to assign codons to amino acids?

Accepted Answer

They used a triplet-binding assay, where synthetic RNA triplets promoted ribosome binding of specific tRNAs carrying radiolabeled amino acids.

Question 19

Which of the following is TRUE regarding the incorporation of selenocysteine and pyrrolysine during translation?

Accepted Answer

They are incorporated at standard stop codons (UGA and UAG) only when specific tRNAs and downstream mRNA sequences are present.

Translation of mRNA: Mechanisms, Components, and Regulation

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