Question 1

Which of the following best describes the role of tRNA during translation?

Accepted Answer

tRNA acts as an adaptor molecule that matches specific amino acids to corresponding mRNA codons via its anticodon.

Question 2

In bacteria, the Shine–Dalgarno sequence is important for which aspect of translation?

Accepted Answer

It base-pairs with the 16S rRNA of the small ribosomal subunit to facilitate initiation.

Question 3

Which enzyme is responsible for attaching amino acids to their corresponding tRNAs, and how many distinct types of this enzyme exist?

Accepted Answer

Aminoacyl tRNA synthetase; there are 20 types, one for each amino acid.

Question 4

During the elongation phase of translation, which ribosomal site holds the tRNA carrying the growing polypeptide chain?

Accepted Answer

P site

Question 5

What is the function of the 23S rRNA in the large ribosomal subunit of bacteria?

Accepted Answer

It catalyzes the formation of peptide bonds between amino acids.

Question 6

Which of the following statements about eukaryotic translation is correct?

Accepted Answer

The 5' cap and poly-A tail of mRNA are both important for translation initiation.

Question 7

A patient with phenylketonuria (PKU) is unable to convert phenylalanine to tyrosine. Which enzyme is defective in this disorder?

Accepted Answer

Phenylalanine hydroxylase

Question 8

The one-gene:one-enzyme hypothesis, developed from studies in Neurospora, was later modified to the one-gene:one-polypeptide hypothesis. What was a key reason for this change?

Accepted Answer

Many proteins are composed of multiple polypeptide chains, each encoded by a different gene.

Question 9

Sickle-cell anemia is caused by a mutation that results in which of the following?

Accepted Answer

A single amino acid substitution in the β-globin chain of hemoglobin.

Question 10

Which of the following best explains why individuals heterozygous for the sickle-cell allele have an advantage in malaria-endemic regions?

Accepted Answer

Their red blood cells are less susceptible to infection by the malaria parasite.

Question 11

Which level of protein structure is defined by the sequence of amino acids in a polypeptide chain?

Accepted Answer

Primary structure

Question 12

What type of chemical reaction forms a peptide bond between two amino acids?

Accepted Answer

Dehydration (condensation) reaction

Question 13

Which of the following is a posttranslational modification that can alter the final protein product?

Accepted Answer

Addition of carbohydrate side chains

Question 14

Diseases such as Creutzfeldt–Jakob disease and bovine spongiform encephalopathy (BSE) are associated with which of the following?

Accepted Answer

Misfolded prion proteins

Question 15

Which of the following best describes a protein domain?

Accepted Answer

A sequence of 50–300 amino acids that folds into a stable, unique conformation and imparts a specific function.

Question 16

Which hypothesis proposes that protein domains originated from ancestral exons brought together by recombination?

Accepted Answer

Exon shuffling hypothesis

Question 17

A mutation prevents the conversion of citrulline to arginine in Neurospora. According to Beadle and Tatum's experiments, what does this indicate?

Accepted Answer

A specific gene is required for the enzyme that catalyzes this step.

Question 18

Which of the following is NOT a function performed by proteins in the cell?

Accepted Answer

Replication of DNA

Question 19

Which of the following equations correctly represents the dehydration reaction that forms a peptide bond between two amino acids?

Accepted Answer

$$\mathrm{Amino\ acid}_1 + \mathrm{Amino\ acid}_2 \rightarrow \mathrm{Dipeptide} + \mathrm{H}_2\mathrm{O}$$

Question 20

Which of the following statements about polyribosomes (polysomes) is correct?

Accepted Answer

They allow multiple ribosomes to translate a single mRNA molecule simultaneously.

Translation and Proteins: Molecular Mechanisms and Genetic Implications

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