Question 1

Which of the following best explains how two cells with the same genome can perform different functions, such as aerial and aquatic vision in a mudskipper's eye?

Accepted Answer

They express different sets of genes due to the presence of specific transcription factors in each cell type.

Question 2

In the trp operon, what role does tryptophan play in regulating gene expression?

Accepted Answer

Tryptophan acts as a corepressor, activating the repressor protein to shut off the operon.

Question 3

Which of the following statements about the lac operon is correct?

Accepted Answer

The lac operon is inducible and is turned on in the presence of lactose.

Question 4

What is the effect of histone acetylation on chromatin structure and gene expression?

Accepted Answer

Histone acetylation loosens chromatin structure, making DNA more accessible for transcription.

Question 5

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

Accepted Answer

An operon is a stretch of DNA that includes a promoter, operator, and genes that are regulated together.

Question 6

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

Accepted Answer

Lactose present, glucose absent, high cAMP, active CRP.

Question 7

What is the primary effect of DNA methylation on gene expression?

Accepted Answer

DNA methylation reduces transcription and can lead to long-term gene silencing.

Question 8

Which of the following is an example of epigenetic inheritance?

Accepted Answer

A methylation pattern on DNA is passed to daughter cells during cell division.

Question 9

How does alternative RNA splicing contribute to protein diversity in eukaryotic cells?

Accepted Answer

By allowing different combinations of exons to be included in the final mRNA, producing different proteins from the same gene.

Question 10

A mutation causes the trp repressor protein to be unable to bind tryptophan. What is the most likely consequence for the trp operon?

Accepted Answer

The trp operon will be constitutively expressed, regardless of tryptophan levels.

Question 11

Which of the following best describes the role of ubiquitin in protein regulation?

Accepted Answer

Ubiquitin tags proteins for degradation by the proteasome.

Question 12

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

Accepted Answer

Eukaryotes regulate gene expression at multiple stages, while prokaryotes mainly regulate at transcription.

Question 13

Which of the following would most likely result from a mutation that prevents the binding of general transcription factors to the promoter in a eukaryotic cell?

Accepted Answer

Transcription initiation would be blocked, and the gene would not be expressed.

Question 14

A scientist observes that a certain gene is only expressed in liver cells but not in lens cells, even though both cell types have the same DNA. What is the most likely explanation?

Accepted Answer

Liver cells have specific activators that bind to the gene's enhancer, while lens cells do not.

Question 15

Which of the following best describes feedback inhibition in the context of tryptophan synthesis?

Accepted Answer

Tryptophan inhibits the activity of the first enzyme in its biosynthetic pathway when present in high concentrations.

Question 16

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

Accepted Answer

Chromatin becomes less compact, allowing transcription factors to access DNA.

Question 17

If a mutation caused the operator of the lac operon to be deleted, what would be the most likely effect?

Accepted Answer

The lac operon would be constitutively expressed, regardless of lactose presence.

Question 18

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

Accepted Answer

Alternative RNA splicing

Question 19

What is the role of the poly-A tail in mRNA stability?

Accepted Answer

It increases mRNA stability, allowing more protein to be produced.

Question 20

Which of the following is an example of combinatorial control of gene activation?

Accepted Answer

Different combinations of activators are required to express different genes in different cell types.

Regulation of Gene Expression: Mechanisms and Examples

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