Question 1

Which of the following best describes the role of cis-acting regulatory sequences in eukaryotic gene expression?

Accepted Answer

They are DNA sequences that regulate transcription of genes located on the same chromosome.

Question 2

In the regulation of the GAL genes in yeast, what is the function of the Gal4 protein in the absence of galactose?

Accepted Answer

Gal4 is bound by Gal80, preventing it from binding to UAS and blocking transcription.

Question 3

Which of the following statements about enhancer sequences is TRUE?

Accepted Answer

Enhancers can regulate genes from a distance, even being located within the gene they regulate.

Question 4

A mutation deletes the locus control region (LCR) near the human $\beta$-globin gene. What is the most likely consequence?

Accepted Answer

Multiple globin genes will be abnormally expressed, potentially causing thalassemia.

Question 5

Which equation best represents the relationship between the number of transcription factors ($TF$) and the number of genes regulated ($G$) in eukaryotes?

Accepted Answer

$G > TF$

Question 6

In the yeast galactose utilization pathway, which molecular event triggers transcription of GAL genes when galactose is present?

Accepted Answer

Gal3 binds Gal80, releasing Gal4 to bind UAS and activate transcription.

Question 7

Which of the following is a function of pioneer factors in eukaryotic gene regulation?

Accepted Answer

They are the first to bind regulatory DNA, facilitating the binding of additional transcription factors.

Question 8

A patient with thalassemia is found to have no mutations in the $\alpha$- or $\beta$-globin genes or their promoters. What is a plausible genetic explanation for their condition?

Accepted Answer

A deletion or rearrangement affecting the locus control region (LCR) near the globin genes.

Question 9

Which of the following best explains tissue-specific expression of the Sonic hedgehog (SHH) gene?

Accepted Answer

Different combinations of regulatory proteins bind distinct enhancers in different tissues.

Question 10

Which of the following is a key difference between cis-acting and trans-acting regulatory elements?

Accepted Answer

Cis-acting elements are DNA sequences that regulate genes on the same chromosome, while trans-acting elements are proteins that can act on any chromosome.

Question 11

Which of the following statements about enhanceosomes is correct?

Accepted Answer

Enhanceosomes direct DNA bending into loops, allowing interaction with RNA polymerase and transcription factors at the promoter.

Question 12

Which scenario best illustrates the modularity of eukaryotic regulatory sequences?

Accepted Answer

An enhancer contains multiple binding sites for different transcription factors, integrating their activities to produce different outputs.

Question 13

Which of the following is TRUE regarding the location of enhancer and silencer sequences?

Accepted Answer

They can be located close to, far upstream, far downstream, or even within the gene they regulate.

Question 14

Which of the following best describes the function of the upstream activator sequence (UAS) in yeast GAL gene regulation?

Accepted Answer

It is an enhancer element that binds Gal4 to activate transcription of GAL genes.

Question 15

Which of the following is a consequence of Gal4 binding to UAS in the presence of galactose?

Accepted Answer

Formation of a multiprotein complex called the Mediator, which induces DNA looping and activates transcription.

Regulation of Gene Expression in Eukaryotes: Key Concepts and Mechanisms

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