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 transcription of genes on the same chromosome, while trans-acting proteins can bind to target sequences on any chromosome.

Question 2

A mutation deletes the locus control region (LCR) upstream of the human β-globin gene complex. What is the most likely consequence?

Accepted Answer

The β-globin complex genes will not be expressed properly during development, leading to abnormal hemoglobin synthesis.

Question 3

Which of the following is a key feature of enhancer sequences in eukaryotic gene regulation?

Accepted Answer

They can function at variable distances from the gene, even within introns or downstream regions.

Question 4

In the yeast GAL system, what is the role of Gal80 in the absence of galactose?

Accepted Answer

Gal80 binds to Gal4, preventing Gal4 from activating transcription of GAL genes.

Question 5

Which of the following best explains how position effect variegation (PEV) can lead to mosaic gene expression in Drosophila?

Accepted Answer

PEV results from the spreading of heterochromatin into euchromatic regions, silencing gene expression in some cells but not others.

Question 6

Which enzyme is responsible for adding acetyl groups to histone tails, and what is the effect of this modification?

Accepted Answer

Histone acetyltransferase (HAT); it relaxes chromatin structure and promotes transcription.

Question 7

A patient with thalassemia is found to have no mutations in the α- or β-globin genes or their promoters. Which regulatory region is most likely mutated?

Accepted Answer

The locus control region (LCR) upstream of the β-globin gene complex.

Question 8

Which of the following statements about epigenetic modifications is FALSE?

Accepted Answer

Epigenetic modifications alter the DNA sequence.

Question 9

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

Accepted Answer

They block the interaction between enhancers and non-target promoters, ensuring specificity of gene regulation.

Question 10

Which of the following is a direct consequence of DNA methylation at CpG islands in the promoter region of a gene?

Accepted Answer

Recruitment of proteins that repress transcription, leading to gene silencing.

Question 11

A mutation in the gene encoding heterochromatin protein 1 (HP-1) in Drosophila leads to which of the following outcomes?

Accepted Answer

Suppression of variegation, resulting in more wild-type gene expression.

Question 12

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

Accepted Answer

Different combinations of regulatory proteins bind to distinct enhancers in different tissues, activating SHH expression in a tissue-specific manner.

Question 13

Which of the following is NOT a feature of open promoters in eukaryotic gene regulation?

Accepted Answer

They require nucleosome displacement for transcription to occur.

Question 14

Which of the following best describes the role of pioneer factors in chromatin remodeling?

Accepted Answer

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

Question 15

Which of the following is a correct statement about genomic imprinting?

Accepted Answer

Only one allele of an imprinted gene is expressed, depending on the parent of origin.

Question 16

Which of the following is a function of the RNA-induced silencing complex (RISC) in RNA interference (RNAi)?

Accepted Answer

It binds to single-stranded guide RNA and directs the destruction or translational repression of target mRNA.

Question 17

Which of the following best describes the effect of histone methylation on gene expression?

Accepted Answer

It can either activate or repress gene expression, depending on the specific lysine residue methylated.

Question 18

A mutation in the imprinting control region (ICR) between the IGF2 and H19 genes on human chromosome 11 leads to loss of methylation on the paternal chromosome. What is the most likely outcome?

Accepted Answer

H19 will be expressed and IGF2 will be silenced on the paternal chromosome.

Question 19

Which of the following is a direct effect of the recruitment of histone deacetylases (HDACs) to a gene promoter?

Accepted Answer

Removal of acetyl groups from histone tails, leading to chromatin condensation and transcriptional repression.

Regulation of Gene Expression in Eukaryotes: Mechanisms and Chromatin Dynamics

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