Question 1

Which of the following best describes the effect of histone acetylation on gene expression in eukaryotes?

Accepted Answer

Histone acetylation decreases the positive charge on histones, loosening their interaction with DNA and increasing gene expression.

Question 2

In the trp operon attenuation mechanism, what happens when tryptophan levels are low in E. coli?

Accepted Answer

The ribosome stalls at the two consecutive trp codons, allowing the 2-3 stem loop to form and preventing the 3-4 terminator loop, so transcription continues.

Question 3

Which chromatin state is associated with transcriptionally active genes in eukaryotes?

Accepted Answer

Euchromatin, which is uncoiled and appears unstained during interphase.

Question 4

A mutation in the GAL4 gene in yeast would most likely result in which of the following outcomes?

Accepted Answer

No transcription of GAL1 and GAL10 genes, even when galactose is present.

Question 5

Which of the following is a function of DNA methylation in eukaryotes?

Accepted Answer

To aid in silencing transcription by changing the binding pattern of transcription factors.

Question 6

Which equation best represents the relationship between mRNA half-life ($$t_{1/2}) $$and gene expression stability in eukaryotes?

Accepted Answer

$$t_{1/2} = \frac{\ln(2)}{k}$$, where $$k is $$the degradation rate constant.

Question 7

Which of the following statements about eukaryotic promoters is correct?

Accepted Answer

The core promoter includes the transcription start site and is required for basal transcription.

Question 8

What is the primary role of the histone variant H2A.Z in eukaryotic gene regulation?

Accepted Answer

It is associated with promoters and enhancers of actively transcribed genes, increasing nucleosome mobility.

Question 9

Which of the following best describes the function of enhancers in eukaryotic transcription?

Accepted Answer

Enhancers can be inverted or located far from the gene and still function to increase transcription.

Question 10

Which of the following is a characteristic of the pre-initiation complex (PIC) in eukaryotic transcription?

Accepted Answer

PIC includes the core promoter, RNA polymerase II, and several general transcription factors.

Question 11

Which DNA-binding motif is commonly found in both eukaryotic and prokaryotic transcription factors?

Accepted Answer

Helix-turn-helix (HTH)

Question 12

A loss-of-function mutation in GAL80 in yeast would most likely result in:

Accepted Answer

Overexpression of GAL1 and GAL10 genes.

Question 13

Which of the following is NOT a level at which eukaryotic gene expression can be regulated?

Accepted Answer

DNA replication

Question 14

Which of the following best explains why eukaryotic gene regulation is more complex than prokaryotic gene regulation?

Accepted Answer

Eukaryotic DNA is associated with histones and other proteins, and genes are processed before export from the nucleus.

Question 15

Which of the following is a correct description of the function of silencers in eukaryotic gene regulation?

Accepted Answer

Silencers repress the level of transcription initiation.

Question 16

Which of the following is true about the default (ground) state of gene expression in eukaryotes?

Accepted Answer

The default state is off, requiring positive regulation to activate transcription.

Question 17

Which of the following best describes the effect of DNA methylation at CpG islands in promoter regions?

Accepted Answer

It decreases transcription by preventing transcription factor binding.

Question 18

Which of the following is a real-world example of gene regulation in response to environmental conditions?

Accepted Answer

Low oxygen levels upregulate erythropoietin expression, increasing red blood cell production.

Question 19

Which of the following statements about the structure of focused promoters is correct?

Accepted Answer

Focused promoters contain a single major transcription start site and include elements such as the TATA box, BRE, and Inr.

Transcriptional Regulation in Eukaryotes: Mechanisms, Chromatin Structure, and Model Systems

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