Question 1

Which of the following best describes the function of the operator in a bacterial operon?

Accepted Answer

It is a DNA sequence that acts as a binding site for repressors or activators, controlling access of RNA polymerase to the genes.

Question 2

In the lac operon, what happens when lactose is present in the environment?

Accepted Answer

Lactose (as allolactose) inactivates the repressor, allowing transcription of the operon.

Question 3

Which of the following statements about the trp operon is correct?

Accepted Answer

It is a repressible operon that is usually on but can be turned off when tryptophan is abundant.

Question 4

Which of the following best explains why gene regulation is essential for multicellular organisms?

Accepted Answer

It enables cells to specialize and perform different functions by expressing different sets of genes.

Question 5

Which of the following is an example of negative control of gene expression in bacteria?

Accepted Answer

The binding of a repressor protein to the operator, preventing transcription.

Question 6

What is the role of cyclic AMP (cAMP) and catabolite activator protein (CAP) in the regulation of the lac operon?

Accepted Answer

CAP, when bound to cAMP, enhances the binding of RNA polymerase to the promoter, increasing transcription when glucose is low.

Question 7

Which of the following modifications is associated with increased gene expression in eukaryotes?

Accepted Answer

Histone acetylation, which loosens chromatin structure

Question 8

A mutation causes a proto-oncogene to become an oncogene. Which of the following is a possible result?

Accepted Answer

The cell cycle is abnormally stimulated, potentially leading to cancer.

Question 9

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

Accepted Answer

They bind to mRNA molecules, leading to mRNA degradation or inhibition of translation.

Question 10

Which of the following scenarios illustrates epigenetic inheritance?

Accepted Answer

Methylation of DNA in a parent leads to gene silencing that is inherited by offspring, without changing the DNA sequence.

Question 11

Which of the following is a key difference between gene regulation in prokaryotes and eukaryotes?

Accepted Answer

Eukaryotes have physically separated transcription and translation, allowing for more regulatory steps.

Question 12

A cell is exposed to a pollutant that increases histone deacetylase (HDAC) activity. What is the most likely effect on gene expression?

Accepted Answer

Gene expression will decrease due to chromatin condensation.

Question 13

Which of the following best explains the role of cytoplasmic determinants in early embryonic development?

Accepted Answer

They are maternal substances unevenly distributed in the egg that influence gene expression in daughter cells.

Question 14

Which of the following is true about tumor-suppressor genes?

Accepted Answer

They normally help prevent uncontrolled cell growth by repairing DNA and inhibiting the cell cycle.

Question 15

A mutation in the p53 gene is most likely to result in which of the following?

Accepted Answer

Failure to suppress the cell cycle in response to DNA damage, increasing cancer risk.

Question 16

Which of the following best describes the process of alternative RNA splicing?

Accepted Answer

It allows a single gene to code for multiple proteins by treating different RNA segments as exons or introns.

Question 17

Which of the following is a likely consequence if an egg lacks the bicoid gene?

Accepted Answer

The embryo will develop with two posterior ends and lack anterior structures.

Question 18

Which of the following is an example of post-translational control of gene expression?

Accepted Answer

Ubiquitin tagging of proteins for degradation by proteasomes.

Question 19

Which of the following best describes the function of enhancers in eukaryotic gene regulation?

Accepted Answer

They are distal control elements that bind activators to increase transcription of specific genes.

Question 20

Which of the following is a real-world example of gene regulation in response to environmental changes?

Accepted Answer

A bacterium increases the expression of genes for lactose metabolism only when lactose is present in its environment.

CH 18 - Regulation of Gene Expression: Mechanisms and Importance

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