Question 1

Which of the following best explains why the default state of transcription in eukaryotes is 'off' while in prokaryotes it is 'on'?

Accepted Answer

Eukaryotic DNA is wrapped around nucleosomes and supercoiled chromatin, making it less accessible for transcription.

Question 2

A mutation prevents the nuclear localization of a transcriptional activator in a specific tissue. What is the most likely outcome?

Accepted Answer

Target genes regulated by this activator will not be expressed in that tissue.

Question 3

Which of the following is a key difference between eukaryotic and prokaryotic gene regulation?

Accepted Answer

Eukaryotic gene regulation relies more on activators, while prokaryotic regulation relies more on repressors.

Question 4

A gene is described as 'poised.' Which of the following best characterizes this state?

Accepted Answer

The gene is accessible and displays both activating and repressing epigenetic markers but is not currently transcribed.

Question 5

Which of the following is NOT a mechanism by which eukaryotic repressors regulate gene expression?

Accepted Answer

Directly binding to the core promoter to block RNA polymerase in all cases.

Question 6

A steroid hormone enters a cell and binds to its receptor. What is the immediate effect on the receptor?

Accepted Answer

The receptor undergoes a conformational change, allowing it to bind DNA and regulate transcription.

Question 7

Which DNA binding domain is most commonly found in homeodomain proteins involved in development?

Accepted Answer

Helix-turn-helix (HTH)

Question 8

A mutation changes the amino acid sequence in the helix of a zinc finger transcription factor. What is the most likely effect?

Accepted Answer

It alters the DNA binding specificity of the transcription factor.

Question 9

Which of the following best describes the role of co-activators in eukaryotic transcription?

Accepted Answer

They do not bind DNA directly but mediate interactions between true activators and the basal transcription apparatus.

Question 10

Which of the following is a real-world example of gene regulation by spatial and temporal control?

Accepted Answer

Hemoglobin gene expression changes during embryonic, fetal, and adult development to reflect different oxygen affinities.

Question 11

Which of the following equations correctly represents the consensus sequence for a classical C2H2 zinc finger?

Accepted Answer

$$\mathrm{Cys}-X_3$-\mathrm{Cys}-X_{4,5}-\mathrm{Phe}-X_2$-\mathrm{Leu}-X_2$-\mathrm{His}-X_3$-\mathrm{His}$$

Question 12

Which of the following best describes the function of architectural proteins in gene regulation?

Accepted Answer

They bind DNA to bring together or separate proteins in a cooperative complex.

Question 13

A patient is exposed to an endocrine disrupting compound that mimics estrogen. What is a likely molecular consequence?

Accepted Answer

The compound binds to estrogen receptors, altering gene expression patterns regulated by estrogen.

Question 14

Which of the following is NOT a way that activator activity can be regulated?

Accepted Answer

By changing the DNA sequence of the core promoter.

Question 15

Which of the following statements about gene-specific transcription regulation is correct?

Accepted Answer

Gene-specific cis-element and trans-factor interactions determine the spatial and temporal pattern of gene expression.

Question 16

Which of the following best describes the function of the activation domain (AD) in a true activator?

Accepted Answer

It binds to the basal transcription apparatus and increases its stability and DNA binding.

Question 17

Which of the following is a property shared by all DNA binding domains (DBDs) of transcription factors?

Accepted Answer

They share a common structural motif but have unique amino acids that determine DNA binding specificity.

Question 18

Which of the following is a correct statement about the regulation of activators?

Accepted Answer

Presence of an activator does not always mean it is active; its ability to bind DNA can be regulated by modifications such as phosphorylation.

Question 19

Which of the following best explains why many weak protein-DNA and protein-protein interactions can lead to strong and specific gene activation?

Accepted Answer

Multiple weak interactions collectively provide specificity and robustness in assembling the transcriptional machinery.

Eukaryotic Transcription Regulation: Mechanisms and Molecular Basis

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