Question 1

Which of the following best describes the function of an operon in prokaryotic gene regulation?

Accepted Answer

A group of genes that are transcribed together and regulated by a single promoter and operator.

Question 2

In the trp operon, what is the role of tryptophan in regulating gene expression?

Accepted Answer

Tryptophan acts as a corepressor, binding to the repressor protein and enabling it to bind the operator, thus turning the operon off.

Question 3

Which of the following scenarios would most likely result in maximal expression of the lac operon in E. coli?

Accepted Answer

Low glucose and high lactose concentrations in the environment.

Question 4

Which of the following best explains why histone acetylation increases gene expression in eukaryotes?

Accepted Answer

Acetylation neutralizes the positive charge on histones, reducing their affinity for DNA and making the DNA more accessible to RNA polymerase.

Question 5

A mutation in the enhancer region of a gene causes the transcription initiation complex to bind less efficiently. What is the most likely outcome?

Accepted Answer

The gene will be transcribed at a lower rate, but the protein product will remain unchanged if splicing and translation are unaffected.

Question 6

Which of the following statements about DNA methylation is correct?

Accepted Answer

DNA methylation typically represses gene expression by making DNA less accessible to transcription factors.

Question 7

Alternative RNA splicing allows a single gene to:

Accepted Answer

Produce multiple different proteins by including or excluding different exons in the final mRNA.

Question 8

A synonymous ("silent") mutation changes the codon from $$\mathrm{GGC} to$$ $$\mathrm{GGG}$$, both coding for glycine. Which of the following could still be affected by this mutation?

Accepted Answer

The splicing of the mRNA, if the mutation disrupts an exonic splicing enhancer (ESE) or suppressor (ESS) site.

Question 9

Which of the following best describes the difference between heterochromatin and euchromatin?

Accepted Answer

Heterochromatin is more tightly packed and generally transcriptionally inactive, while euchromatin is less compact and transcriptionally active.

Question 10

In eukaryotic cells, which of the following is a direct consequence of DNA methylation at CpG islands near promoter regions?

Accepted Answer

Transcription of the associated gene is repressed.

Question 11

Which of the following is a likely effect of excessive histone deacetylation on a tumor suppressor gene?

Accepted Answer

Reduced expression of the tumor suppressor gene, potentially contributing to uncontrolled cell growth.

Question 12

A patient with Duchenne muscular dystrophy (DMD) has a deletion of exon 50 in the dystrophin gene. Which therapeutic strategy is used to restore the reading frame and allow some dystrophin production?

Accepted Answer

Exon skipping therapy, which causes the splicing machinery to skip exon 51, restoring the reading frame.

Question 13

Which of the following best explains why bacterial genes cannot be directly used to produce human insulin in bacteria without modification?

Accepted Answer

Bacterial cells cannot splice out introns, so the human insulin gene must be modified to contain only exons.

Question 14

Which of the following is true regarding the regulation of gene expression in eukaryotes compared to prokaryotes?

Accepted Answer

Eukaryotes have more complex regulation, including chromatin remodeling, alternative splicing, and multiple levels of control.

Question 15

A mutation in a master regulatory gene during embryonic development is most likely to:

Accepted Answer

Alter the fate of multiple cell types, potentially leading to major developmental abnormalities.

Question 16

Which of the following best describes the role of transcription factors in eukaryotic gene expression?

Accepted Answer

They bind to specific DNA sequences (such as promoters and enhancers) to regulate the recruitment of RNA polymerase and control transcription.

Question 17

If a gene is highly methylated in a differentiated skin cell but not in a stem cell, what is the most likely explanation?

Accepted Answer

The gene is silenced in the skin cell but remains potentially active in the stem cell.

Question 18

Which of the following is a direct effect of phosphorylation of a translation initiation factor in eukaryotic cells?

Accepted Answer

Inhibition of translation by preventing mRNA from binding to the ribosome.

Regulation of Gene Expression: Foundations and Mechanisms

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