Question 1

Which of the following best describes the function of an operon in prokaryotic gene regulation?

Accepted Answer

A cluster of functionally related genes regulated by a single 'on-off switch' called an operator.

Question 2

In the trp operon, what is the role of tryptophan?

Accepted Answer

It acts as a corepressor that activates the repressor, shutting off the operon.

Question 3

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

Accepted Answer

Low glucose, high lactose

Question 4

Which of the following statements about histone acetylation is correct?

Accepted Answer

It loosens chromatin structure, promoting transcription initiation.

Question 5

A mutation in the regulatory gene of the lac operon results in a repressor that cannot bind allolactose. What is the most likely outcome?

Accepted Answer

The lac operon will be permanently turned off, even in the presence of lactose.

Question 6

Which of the following best explains why different cell types in a multicellular organism can have different functions, even though they contain the same DNA?

Accepted Answer

Differential gene expression leads to the production of different proteins in each cell type.

Question 7

Which of the following is an example of epigenetic inheritance?

Accepted Answer

DNA methylation patterns that silence a gene and are inherited by daughter cells.

Question 8

What is the primary function of microRNAs (miRNAs) in eukaryotic cells?

Accepted Answer

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

Question 9

A patient is found to have a mutation in the p53 gene. Which of the following is a likely consequence?

Accepted Answer

Decreased ability to suppress the cell cycle, increasing cancer risk.

Question 10

Which of the following best describes the process of alternative RNA splicing?

Accepted Answer

The production of different mRNA molecules from the same primary transcript by including or excluding certain exons.

Question 11

Which of the following is a direct result of DNA methylation?

Accepted Answer

Long-term inactivation of the methylated gene.

Question 12

In the context of cancer, what is an oncogene?

Accepted Answer

A mutated proto-oncogene that promotes uncontrolled cell division.

Question 13

Which of the following mechanisms allows a single gene to code for multiple proteins in eukaryotes?

Accepted Answer

Alternative RNA splicing

Question 14

Which of the following is true regarding the role of CRP (cAMP receptor protein) in the regulation of the lac operon?

Accepted Answer

CRP, when bound to cAMP, increases the affinity of RNA polymerase for the promoter, enhancing transcription when glucose is scarce.

Question 15

A scientist uses RNA interference (RNAi) to study gene function in a laboratory. Which molecule is most directly involved in this process?

Accepted Answer

Small interfering RNA (siRNA)

Question 16

Which of the following best explains why elephants have a lower cancer rate compared to humans?

Accepted Answer

They have more copies of the p53 tumor suppressor gene.

Question 17

Which of the following is a function of tumor-suppressor proteins?

Accepted Answer

Repair damaged DNA and inhibit the cell cycle.

Question 18

Which of the following is an example of positive gene regulation?

Accepted Answer

CRP binding to the promoter to increase RNA polymerase binding and transcription.

Question 19

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 and cell fate.

Question 20

A mutation in a maternal effect gene in Drosophila results in embryos lacking anterior structures. Which gene is most likely mutated?

Accepted Answer

bicoid

Regulation of Gene Expression: Mechanisms and Biological Significance

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