Question 1

Which of the following best describes the role of pioneer transcription factors in gene regulation?

Accepted Answer

They can bind to their DNA target sites even when those sites are wrapped in nucleosomes, initiating chromatin opening.

Question 2

A researcher observes that a gene is highly expressed in liver cells but silent in neurons. Which epigenetic modification is most likely responsible for the gene's silencing in neurons?

Accepted Answer

DNA methylation at CpG islands upstream of the gene's promoter

Question 3

Which enzyme is responsible for adding acetyl groups to histone tails, and what is the effect on gene expression?

Accepted Answer

Histone acetyltransferase (HAT); increases gene expression by opening chromatin

Question 4

Which of the following equations correctly represents the conversion of cytosine to 5-methylcytosine by DNA methyltransferase?

Accepted Answer

$$\mathrm{Cytosine} + \mathrm{CH}_3 \rightarrow \mathrm{5{-}methylcytosine}$$

Question 5

A mutation in the SWI/SNF complex would most likely result in which of the following outcomes?

Accepted Answer

Reduced ability to reposition nucleosomes, leading to decreased gene expression

Question 6

Which of the following best explains why histone deacetylation is associated with gene repression?

Accepted Answer

Deacetylation removes acetyl groups, causing chromatin to become more compact and less accessible to transcription machinery.

Question 7

In the context of the Dutch Hunger Winter, what was the observed long-term epigenetic effect on individuals conceived during the famine?

Accepted Answer

Decreased methylation of the IGF2 gene, leading to altered metabolic phenotypes

Question 8

Which of the following statements about RNA interference (RNAi) is correct?

Accepted Answer

RNAi involves small double-stranded RNAs that guide the RISC complex to degrade or block translation of complementary mRNAs.

Question 9

Which of the following is a plausible consequence of maternal exposure to Bisphenol A (BPA) in mice, as discussed in epigenetic studies?

Accepted Answer

Decreased CpG methylation upstream of the Agouti gene, resulting in more yellow, obese offspring

Question 10

Which of the following best describes the difference between euchromatin and heterochromatin?

Accepted Answer

Euchromatin is generally acetylated and transcriptionally active, while heterochromatin is methylated and transcriptionally silent.

Question 11

A scientist introduces a double-stranded RNA (dsRNA) corresponding to a specific gene into a eukaryotic cell. What is the most likely outcome?

Accepted Answer

The dsRNA will be processed into siRNAs, which will guide the RISC complex to degrade the target mRNA, reducing gene expression.

Question 12

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

Accepted Answer

Eukaryotic genes are often regulated by chromatin structure and histone modifications, while prokaryotic genes are not.

Question 13

Which of the following best explains how histone acetylation can be reversed?

Accepted Answer

Histone deacetylases (HDACs) remove acetyl groups from histone tails, leading to chromatin condensation and gene repression.

Question 14

A gene is found to be transcriptionally silent and its promoter region is resistant to DNase I digestion. Which chromatin state is most likely present?

Accepted Answer

Closed chromatin with deacetylated and methylated histones

Question 15

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

Accepted Answer

Recruitment of proteins that bind methylated DNA and attract histone deacetylases, leading to gene repression

Question 16

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

Accepted Answer

They bind to complementary mRNAs and either degrade them or block their translation.

Question 17

A mouse is born to a mother that was not groomed or licked frequently as a pup. Which of the following is a likely outcome based on epigenetic studies?

Accepted Answer

Increased methylation of the glucocorticoid receptor gene and increased anxiety-like behavior

Question 18

Which of the following is an example of an epigenetic change?

Accepted Answer

Methylation of cytosine residues in DNA without altering the DNA sequence

Regulation of Gene Expression in Eukaryotes: Chromatin, Epigenetics, and Small RNAs

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