Question 1

Which of the following best describes the function of a repressor protein in the regulation of gene expression in prokaryotes?

Accepted Answer

It binds to the operator and blocks RNA polymerase from transcribing the genes.

Question 2

In the trp operon, what happens when tryptophan is present in high concentrations?

Accepted Answer

Tryptophan binds to the repressor, activating it and shutting off the operon.

Question 3

Which of the following is true about the lac operon in E. coli?

Accepted Answer

The lac operon is an inducible operon that is usually off unless lactose is present.

Question 4

Which molecule acts as the inducer for the lac operon?

Accepted Answer

Allolactose

Question 5

What is the effect of histone acetylation on gene expression?

Accepted Answer

It opens chromatin structure, promoting transcription.

Question 6

Which of the following best explains epigenetic inheritance?

Accepted Answer

It involves inheritance of traits through chromatin modifications that do not alter the DNA sequence.

Question 7

A mutation in the operator sequence of the trp operon prevents the repressor from binding. What is the most likely outcome?

Accepted Answer

The operon will be permanently on, and the genes for tryptophan synthesis will always be transcribed.

Question 8

Which of the following is a direct result of alternative RNA splicing?

Accepted Answer

A single gene can code for multiple proteins.

Question 9

How do microRNAs (miRNAs) regulate gene expression?

Accepted Answer

By binding to mRNA and causing its degradation or blocking its translation.

Question 10

Which of the following best describes the role of cytoplasmic determinants in embryonic development?

Accepted Answer

They are maternal substances in the egg that influence early gene expression in the embryo.

Question 11

What is the primary function of proteasomes in the cell?

Accepted Answer

To degrade proteins that have been tagged with ubiquitin.

Question 12

Which of the following scenarios would most likely result in the highest level of lac operon transcription in E. coli?

Accepted Answer

Low glucose, high lactose

Question 13

Which of the following statements about enhancers is correct?

Accepted Answer

They are distal control elements that can increase the rate of transcription when bound by activators.

Question 14

A scientist uses RNA interference (RNAi) to study gene function in yeast. Which type of RNA is most directly involved in this process?

Accepted Answer

siRNA

Question 15

Which of the following best explains why identical twins can have different susceptibilities to genetically based diseases?

Accepted Answer

They may have different epigenetic modifications affecting gene expression.

Question 16

Which of the following is an example of positive gene regulation in the lac operon?

Accepted Answer

Binding of CRP (cAMP receptor protein) to the promoter region when glucose is scarce.

Question 17

Which process is responsible for the long-term inactivation of genes during cellular differentiation?

Accepted Answer

DNA methylation

Question 18

What is the main outcome of pattern formation during animal development?

Accepted Answer

The establishment of the major body axes and spatial organization of tissues and organs.

Question 19

Which of the following is a likely consequence if a mutation prevents the addition of ubiquitin to a protein?

Accepted Answer

The protein will persist longer in the cell because it is not targeted for degradation.

Question 20

Which of the following best describes the role of bicoid mRNA in Drosophila embryonic development?

Accepted Answer

It is localized at the anterior end and establishes the anterior-posterior axis.

Regulation of Gene Expression in Prokaryotes and Eukaryotes

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