Question 1

Which of the following best describes the difference between cis-acting regulatory sequences and trans-acting regulatory proteins in eukaryotic gene regulation?

Accepted Answer

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

Question 2

A mutation deletes an enhancer located 1 million base pairs upstream of the Sonic Hedgehog (SHH) gene. Which of the following is the most likely consequence?

Accepted Answer

The SHH gene will fail to be expressed in specific tissues, such as developing limbs, but may still be expressed in other tissues.

Question 3

Which of the following best explains the molecular mechanism of position-effect variegation (PEV) in Drosophila?

Accepted Answer

A gene is relocated near heterochromatin, which can spread and silence the gene in some cells but not others.

Question 4

Which chemical modification is most directly associated with the conversion of chromatin to a more open, transcriptionally active state?

Accepted Answer

Histone acetylation of lysine residues

Question 5

A researcher finds that a gene is not expressed because its promoter region is heavily methylated at CpG dinucleotides. What is the most likely effect of this methylation?

Accepted Answer

The promoter structure is closed, and transcription is repressed.

Question 6

Which of the following statements about the SWI/SNF chromatin remodeling complex is correct?

Accepted Answer

It displaces nucleosomes to uncover promoters and enhancers, facilitating transcription.

Question 7

In the context of the GAL gene system in yeast, what is the role of the Gal4 protein when galactose is present?

Accepted Answer

Gal4 binds to UASg and activates transcription of GAL genes.

Question 8

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

Accepted Answer

They prevent enhancers from activating non-target genes by blocking the spread of enhancer activity.

Question 9

A patient with a form of thalassemia is found to have a deletion in the locus control region (LCR) upstream of the β-globin gene cluster. What is the most likely molecular consequence?

Accepted Answer

Loss of coordinated, stage-specific expression of β-globin genes, leading to anemia.

Question 10

Which of the following is a key feature of epigenetic modifications?

Accepted Answer

They are reversible and do not change the DNA sequence, but can be transmitted during cell division.

Question 11

Which of the following best explains the mechanism of X-chromosome inactivation in female mammals?

Accepted Answer

A long non-coding RNA (lncRNA) from the Xist gene coats the X chromosome to be inactivated, recruiting chromatin-modifying complexes.

Question 12

Which of the following is true regarding genomic imprinting?

Accepted Answer

Imprinting involves epigenetic marks that silence one allele depending on its parental origin.

Question 13

Which of the following best describes the outcome of RNA interference (RNAi) when the guide strand is a perfect match to its target mRNA?

Accepted Answer

The guide RNA complex degrades the target mRNA.

Question 14

A scientist introduces double-stranded RNA (dsRNA) corresponding to a specific gene into a plant cell. Which of the following is the most likely result?

Accepted Answer

Suppression of both the introduced gene and the endogenous gene via RNAi.

Question 15

Which of the following is a function of long non-coding RNAs (lncRNAs) in eukaryotic gene regulation?

Accepted Answer

They serve as scaffolds linking regulatory proteins to affect gene expression.

Question 16

Which of the following best describes the 'histone code' hypothesis?

Accepted Answer

Combinations of chemical modifications to histone tails specify distinct chromatin states and gene expression patterns.

Question 17

A yeast gene is repressed when nucleosomes block access to its promoter and UAS (upstream activator sequence). Which chromatin modification would most likely activate this gene?

Accepted Answer

Acetylation of histone tails at the promoter, leading to nucleosome displacement.

Question 18

Which of the following is a direct effect of DNA methylation at CpG islands in gene promoters?

Accepted Answer

Repression of gene transcription by closing chromatin structure.

Question 19

Which of the following best explains how small RNAs (such as siRNAs and miRNAs) can regulate gene expression at the chromatin level?

Accepted Answer

They guide chromatin-modifying enzymes to specific DNA regions, leading to heterochromatin formation and transcriptional silencing.

Regulation of Eukaryotic Gene Expression (Chapter 13 Study Notes)

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