Trp Operon Attenuation Quiz Year 12 Biology VCE

What is the primary function of the trp operon in bacteria?

• To produce enzymes for glucose metabolism

• To synthesize tryptophan when it is not available in the environment

• To break down lactose into glucose and galactose

• To regulate the amount of glucose entering the cell

Answer explanation

The primary function of the trp operon in bacteria is to synthesize tryptophan when it is not available in the environment.

How does the presence of tryptophan affect the trp operon?

• It activates the operon, increasing the production of tryptophan

• It has no effect on the operon

• It represses the operon, decreasing the production of tryptophan

• It changes the operon's structure, making it inactive

Answer explanation

Tryptophan represses the trp operon, decreasing the production of tryptophan.

What is the role of the leader peptide in trp operon attenuation?

• It binds to tryptophan and activates the operon

• It is involved in the termination of transcription under certain conditions

• It transports tryptophan into the cell

• It acts as a repressor protein

Answer explanation

The leader peptide is involved in the termination of transcription under certain conditions, leading to the attenuation of the trp operon.

Which of the following is a key feature of the mechanism of trp operon attenuation?

• The binding of a repressor protein to the operator

• The formation of a stem-loop structure in the mRNA

• The phosphorylation of enzymes involved in tryptophan synthesis

• The activation of a secondary operon

Answer explanation

The key feature of the mechanism of trp operon attenuation is the formation of a stem-loop structure in the mRNA, which regulates the expression of the operon.

How does high levels of tryptophan influence the attenuation mechanism of the trp operon?

• It promotes the formation of a transcriptional pause loop

• It prevents the formation of the stem-loop structure in the mRNA

• It facilitates the formation of a terminator stem-loop, halting transcription

• It activates alternative pathways for tryptophan synthesis

Answer explanation

High levels of tryptophan facilitate the formation of a terminator stem-loop, halting transcription, which is the attenuation mechanism of the trp operon.

What effect does a mutation in the trp operon leader sequence that prevents the formation of the stem-loop structure have?

• It increases the sensitivity of the operon to tryptophan levels

• It has no effect on the operon's function

• It leads to continuous transcription of the trp operon, regardless of tryptophan levels

• It decreases the rate of tryptophan synthesis

Answer explanation

A mutation preventing the stem-loop structure leads to continuous transcription of the trp operon, regardless of tryptophan levels.

Why is the trp operon considered a model for understanding gene regulation in prokaryotes?

• Because it is the only operon present in all bacteria

• Because it involves both transcriptional and translational control mechanisms

• Because it is the simplest form of gene regulation

• Because it regulates the synthesis of all amino acids

Answer explanation

The trp operon is considered a model for understanding gene regulation in prokaryotes because it involves both transcriptional and translational control mechanisms.

What is the significance of the trp operon attenuation in gene expression?

• It demonstrates the role of environmental factors in gene regulation

• It shows how genetic mutations can affect protein synthesis

• It illustrates a mechanism by which cells conserve energy and resources

• It provides evidence for the theory of evolution

Answer explanation

The significance of the trp operon attenuation in gene expression is that it illustrates a mechanism by which cells conserve energy and resources.

Which of the following mutations would likely have the least impact on trp operon attenuation?

• A mutation in the trp operon promoter region

• A mutation in the leader peptide coding sequence that does not affect the formation of stem-loop structures

• A mutation that increases the affinity of the repressor protein for tryptophan

• A mutation in the ribosome binding site of the trp operon genes

Answer explanation

A mutation in the leader peptide coding sequence that does not affect the formation of stem-loop structures would likely have the least impact on trp operon attenuation because it would not interfere with the regulatory mechanism.

How does the trp operon ensure that tryptophan is synthesized only when needed?

• By activating transcription in the presence of tryptophan

• By degrading mRNA when tryptophan is abundant

• By attenuating transcription when tryptophan levels are high

• By increasing the degradation rate of tryptophan when it is not needed

Answer explanation

The trp operon ensures that tryptophan is synthesized only when needed by attenuating transcription when tryptophan levels are high.