Question 1

Which of the following best describes the primary mechanism by which eukaryotic cells regulate gene expression?

Accepted Answer

Regulation of transcription initiation

Question 2

A researcher observes that a gene is not expressed in a particular cell type, even though the gene is present in the genome. The chromatin in this region is highly condensed. Which process most likely explains this observation?

Accepted Answer

DNA methylation

Question 3

Which enzyme is responsible for adding methyl groups to cytosine bases in DNA, leading to gene silencing?

Accepted Answer

DNA methyltransferase

Question 4

A mutation causes the loss of function of a methyl-CpG-binding protein. What is the most likely consequence?

Accepted Answer

Failure to recruit histone deacetylase, resulting in less chromatin compaction and increased gene expression

Question 5

Which of the following is a direct effect of histone acetylation?

Accepted Answer

Decreased binding of DNA to histones, resulting in more open chromatin

Question 6

A scientist is studying a gene with a CpG island near its promoter. In liver cells, the CpG island is methylated, but in muscle cells, it is not. What is the most likely outcome?

Accepted Answer

The gene is silenced in liver cells and expressed in muscle cells

Question 7

Which of the following best explains how steroid hormones regulate gene expression?

Accepted Answer

They bind to intracellular receptors, which then act as regulatory transcription factors

Question 8

Which of the following motifs is commonly found in the DNA-binding domains of regulatory transcription factors?

Accepted Answer

Helix-turn-helix

Question 9

Alternative RNA splicing allows for:

Accepted Answer

The production of multiple protein isoforms from a single gene

Question 10

Which of the following mechanisms can rapidly decrease the concentration of a specific mRNA in the cytoplasm?

Accepted Answer

Shortening of the polyA tail

Question 11

A mutation in the AU-rich element (ARE) of an mRNA's 3' untranslated region would most likely:

Accepted Answer

Increase the stability of the mRNA

Question 12

Which of the following is a function of microRNAs (miRNAs) in eukaryotic cells?

Accepted Answer

They bind to mRNA and either degrade it or block its translation

Question 13

In the experiment by Fire and Mello (1998) in C. elegans, what was the effect of injecting double-stranded RNA corresponding to the mex-3 gene?

Accepted Answer

Potent and specific degradation of mex-3 mRNA

Question 14

Which of the following best describes the role of the proteasome in gene expression regulation?

Accepted Answer

It degrades ubiquitinated proteins, controlling protein levels post-translationally

Question 15

A gene is expressed only when an activator protein binds to an enhancer element. What would happen if the enhancer is methylated?

Accepted Answer

The activator protein would be unable to bind, and gene expression would decrease

Question 16

Which of the following is a direct result of the recruitment of histone deacetylase to a methylated CpG island?

Accepted Answer

Chromatin becomes more compact, repressing gene expression

Question 17

Which of the following best explains why most cells in a multicellular organism are genetically identical but functionally different?

Accepted Answer

Differential gene expression

Question 18

Which of the following equations best represents the relationship between mRNA concentration $$[mRNA]$$, rate of synthesis $$r_s$$, and rate of degradation $$r_d at $$steady state?

Accepted Answer

$$[mRNA] = r_s / r_d$$

Question 19

Which of the following is a plausible reason why double-stranded RNA can silence gene expression in plants and animals?

Accepted Answer

It triggers the RNA-induced silencing complex (RISC) to degrade complementary mRNA

Question 20

Which of the following statements about genomic imprinting is correct?

Accepted Answer

It results in the expression of only one parental allele due to DNA methylation

Regulation of Gene Expression in Eukaryotes

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