Question 1

Which of the following best describes the role of enhancers in eukaryotic gene regulation?

Accepted Answer

Enhancers are DNA sequences that can increase transcription rates by binding activator proteins, and they can be located upstream, downstream, or even within introns of the gene they regulate.

Question 2

A mutation causes the loss of function of a histone acetyltransferase enzyme in a eukaryotic cell. What is the most likely effect on gene expression?

Accepted Answer

Gene expression will decrease because DNA will remain tightly wound around histones, making promoters less accessible to transcription factors.

Question 3

Which of the following sequences is most likely to be found immediately upstream of a eukaryotic gene and is essential for the binding of general transcription factors?

Accepted Answer

The core promoter, which often contains a TATA box sequence.

Question 4

In the process of eukaryotic transcription initiation, which of the following is the correct order of events?

Accepted Answer

Activators bind to enhancers, chromatin remodeling complexes open chromatin, general transcription factors bind to the promoter, RNA polymerase binds, and transcription begins.

Question 5

Which of the following best explains why alternative splicing is important in eukaryotic cells?

Accepted Answer

It allows a single gene to produce multiple different proteins by including or excluding different exons in the final mRNA.

Question 6

A researcher finds that a certain mRNA is rapidly degraded in the cytoplasm, resulting in low levels of the corresponding protein. Which regulatory mechanism is most likely responsible for this observation?

Accepted Answer

The mRNA has a short lifespan due to decreased stability, possibly regulated by microRNAs that target it for degradation.

Question 7

Which of the following statements about silencers is correct?

Accepted Answer

Silencers are DNA sequences that bind repressor proteins to decrease or shut down transcription, representing negative control.

Question 8

In eukaryotic cells, what is the function of the mediator complex during transcription initiation?

Accepted Answer

It acts as a bridge between activator proteins bound to enhancers and the general transcription machinery at the promoter.

Question 9

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

Accepted Answer

Eukaryotes package their DNA into chromatin, requiring chromatin remodeling for gene expression, while prokaryotes do not.

Question 10

A eukaryotic cell needs to quickly stop the production of a specific protein. Which mechanism would be the most energy-efficient way to achieve this?

Accepted Answer

Degrading the mRNA in the cytoplasm using microRNAs to prevent further translation.

Question 11

Which of the following best describes the function of general transcription factors in eukaryotic transcription?

Accepted Answer

They bind to the core promoter (such as the TATA box) and help recruit RNA polymerase to initiate transcription.

Question 12

A gene contains 14 exons. In skeletal muscle cells, exons 2 and 13 are included in the mature mRNA, but in brain cells, these exons are excluded. What process is responsible for this difference?

Accepted Answer

Alternative splicing

Question 13

Which of the following equations best represents the relationship between the number of genes ($$G$$), the number of alternative splicing patterns per gene ($$S$$), and the maximum number of different proteins ($$P) $$that can be produced?

Accepted Answer

$$P = G 	imes S$$

Question 14

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

Accepted Answer

Decreased positive charge on histones, leading to relaxed chromatin and increased gene expression.

Question 15

A scientist introduces a mutation that prevents the formation of DNA loops between enhancers and promoters. What is the most likely consequence?

Accepted Answer

Transcription of the associated gene will decrease because activators cannot effectively interact with the transcription machinery.

Question 16

Which of the following best describes the process of RNA interference (RNAi) mediated by microRNAs in eukaryotic cells?

Accepted Answer

MicroRNAs bind to complementary sequences on target mRNAs, leading to their degradation or inhibition of translation.

Question 17

Which of the following is NOT a step in the initiation of transcription in eukaryotic cells?

Accepted Answer

RNA polymerase synthesizes the poly-A tail on the mRNA.

Question 18

If a eukaryotic cell expresses a gene only in response to a specific signal, which regulatory element is most likely involved?

Accepted Answer

An enhancer that binds an activator protein present only when the signal is present.

Question 19

Which of the following statements about mRNA stability is correct?

Accepted Answer

The longer an mRNA persists in the cytoplasm, the more protein can be produced from it.

Eukaryotic Gene Expression: Regulation and Control Mechanisms

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