Question 1

Which of the following best explains how different cell types (e.g., neurons and muscle cells) can arise in the human body, even though all cells contain the same DNA?

Accepted Answer

Gene regulation allows selective expression of genes, resulting in different proteins and cell functions.

Question 2

A researcher discovers a gene that produces a functional RNA molecule but is never translated into protein. Which type of gene is this most likely to be?

Accepted Answer

A noncoding RNA gene

Question 3

Which of the following statements about the human genome is correct?

Accepted Answer

Repetitive DNA constitutes approximately 50% of the genome.

Question 4

Which of the following best describes the function of microRNAs (miRNAs) in eukaryotic cells?

Accepted Answer

They regulate gene expression by blocking translation and promoting RNA degradation.

Question 5

During eukaryotic transcription initiation, which event occurs first?

Accepted Answer

TBP (TATA-binding protein) binds to the TATA box in the promoter.

Question 6

A mutation in the AAUAAA sequence of a pre-mRNA would most likely affect which process?

Accepted Answer

Polyadenylation at the 3′ end

Question 7

Which of the following statements about RNA polymerase is TRUE?

Accepted Answer

RNA polymerase does not require helicase to unwind DNA during transcription.

Question 8

A patient is exposed to α-amanitin, a toxin from poisonous mushrooms. Which cellular process will be most directly inhibited?

Accepted Answer

Transcription of protein-coding genes by RNA Polymerase II

Question 9

Which of the following best explains why alternative splicing increases protein diversity in humans?

Accepted Answer

It allows a single gene to produce multiple mRNAs with different combinations of exons.

Question 10

A frameshift mutation is most likely to result from which of the following genetic changes?

Accepted Answer

Insertion or deletion of a number of nucleotides not divisible by 3

Question 11

Which of the following best describes the role of the 5′ cap added to eukaryotic mRNA?

Accepted Answer

It is required for nuclear export, protects RNA from degradation, and promotes translation initiation.

Question 12

Which of the following statements about the genetic code is correct?

Accepted Answer

The code is universal and redundant, with 61 codons specifying amino acids.

Question 13

A scientist is studying a ribosome and observes that a tRNA is located in the A site. What is the next step in translation elongation?

Accepted Answer

Peptidyl transferase will catalyze peptide bond formation between the amino acid in the A site and the growing chain in the P site.

Question 14

Which of the following antibiotics specifically inhibits bacterial RNA polymerase, thereby blocking transcription in prokaryotes?

Accepted Answer

Rifamycin

Question 15

A mutation changes a codon from UAU (tyrosine) to UAA. What type of mutation is this, and what is its likely effect?

Accepted Answer

Nonsense mutation; introduces a premature stop codon

Question 16

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

Accepted Answer

They attach the correct amino acid to its corresponding tRNA using ATP.

Question 17

A patient is treated with tetracycline for a bacterial infection. Which step of gene expression in the pathogen is directly inhibited?

Accepted Answer

Binding of aminoacyl-tRNA to the ribosomal A site during translation

Question 18

Which of the following is a direct consequence of a mutation that disrupts normal RNA splicing in a gene?

Accepted Answer

The mature mRNA may contain introns, potentially leading to abnormal or nonfunctional proteins.

Question 19

Which of the following best explains why the third position of a codon is called the 'wobble' position?

Accepted Answer

It allows non-standard base pairing, enabling one tRNA to recognize multiple codons.

Question 20

A scientist is analyzing a eukaryotic cell and finds that a large number of misfolded proteins are accumulating. Which cellular structure is most likely malfunctioning?

Accepted Answer

Proteasome

Gene Expression: From DNA to Functional Protein

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