Question 1

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

Accepted Answer

A cluster of genes under the control of a single promoter, allowing coordinated expression of related proteins.

Question 2

In the trp operon, what is the role of tryptophan when cellular levels are high?

Accepted Answer

Tryptophan acts as a corepressor, activating the repressor to bind the operator and inhibit transcription.

Question 3

Which scenario will result in maximal expression of the lac operon in E. coli?

Accepted Answer

Low glucose and high lactose present.

Question 4

Which of the following statements about repressors in negative control of gene expression is correct?

Accepted Answer

Repressors are regulatory proteins that bind to the operator, blocking RNA polymerase from initiating transcription.

Question 5

A mutation in the operator region of the lac operon prevents the repressor from binding. What is the most likely outcome?

Accepted Answer

The lac operon will be constitutively expressed, even in the absence of lactose.

Question 6

Which of the following best explains the role of cAMP and CRP (CAP) in the regulation of the lac operon?

Accepted Answer

The cAMP-CRP complex enhances RNA polymerase binding to the promoter under low glucose conditions.

Question 7

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

Accepted Answer

Prokaryotes use operons for coordinated gene expression, while eukaryotes typically regulate genes individually.

Question 8

Which of the following elements is NOT typically part of the basal transcription complex in eukaryotes?

Accepted Answer

Enhancer-binding activators

Question 9

A mutation eliminates the iron response element (IRE) in the 5'-UTR of ferritin mRNA. What is the most likely effect on ferritin synthesis under low iron conditions?

Accepted Answer

Ferritin synthesis will be abnormally high because translation is no longer inhibited.

Question 10

Which of the following best describes the mechanism by which SREBP regulates HMG-CoA reductase expression?

Accepted Answer

SREBP undergoes proteolytic cleavage in the Golgi, releasing a domain that translocates to the nucleus to activate gene expression.

Question 11

Which of the following is true regarding the regulation of translation by eIF2 in reticulocytes?

Accepted Answer

High heme levels prevent phosphorylation of eIF2, allowing translation of globin.

Question 12

Which of the following statements about the regulation of the PEPCK gene is correct?

Accepted Answer

The 5'-flanking region of the PEPCK gene contains multiple response elements for hormones such as glucocorticoids, thyroid hormone, and insulin.

Question 13

Which of the following best explains why the transferrin receptor mRNA is stabilized in low iron conditions?

Accepted Answer

IRE-BP binds to IREs at the 3'-end of the mRNA, preventing its degradation.

Question 14

Which of the following is a direct effect of AMP-activated protein kinase (AMPK) on HMG-CoA reductase?

Accepted Answer

AMPK phosphorylates and inactivates HMG-CoA reductase, decreasing cholesterol synthesis.

Question 15

A patient has a mutation that prevents the binding of IRE-BP to the IRE in ferritin mRNA. What is the most likely consequence under low iron conditions?

Accepted Answer

Ferritin translation will proceed, leading to unnecessary iron storage.

Question 16

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

Accepted Answer

Enhancers are DNA sequences that increase gene expression by binding activator proteins, often at a distance from the promoter.

Question 17

Which of the following is a consequence of high cholesterol levels on HMG-CoA reductase regulation?

Accepted Answer

High cholesterol levels promote the oligomerization of HMG-CoA reductase membrane domains, leading to decreased enzyme activity.

Question 18

Which of the following best explains the 'all-or-none' regulation of genes within a prokaryotic operon?

Accepted Answer

All genes in the operon are transcribed together as a single polycistronic mRNA, resulting in coordinated expression.

Regulation of Gene Expression: Prokaryotic and Eukaryotic Mechanisms

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