Regulatory Mechanisms in Gene Expression

Identify the components labelled 'O' and 'P'.

• Operator, Promoter

• Promoter, Operator

• Leader, Attenuator

• Structural genes, Regulatory region

The structure labelled 'O' provides a binding site for which of the following in regulating expression of structural genes?

• RNA polymerase

• Repressor

• Translation initiator

• Gene expression enhancer

The function of the structure labelled 'P' is to:

• Enhance gene expression

• Provide a binding site for a repressor

• Provide a binding site for RNA polymerase

• Terminate transcription

Repression and attenuation are similar in that they both:

• increase trp production

• conserve energy for the cell

• turn the structural genes off/on

• enhance gene expression

What happens to the repressor protein when tryptophan is low in the bacterial environment?

• It binds to the operator.

• It remains inactive.

• It changes shape.

• It binds to the promoter.

In the presence of low tryptophan, what does RNA polymerase do in repression?

• It detaches from the DNA.

• It binds to the operator.

• It binds to the promoter.

• It stops transcription.

What occurs in attenuation when tryptophan is low?

• Transcription is blocked.

• RNA polymerase detaches.

• Hairpin forms earlier in the leader region.

• Repressor binds to the operator.

When tryptophan is high, what binds to the repressor protein in repression?

• One tryptophan molecule.

• Two tryptophan molecules.

• RNA polymerase.

• Leader region.

What is the effect on transcription when tryptophan is high in repression?

• Transcription continues.

• Transcription is blocked.

• Transcription is enhanced.

• Transcription is paused.

What forms later in the leader region during attenuation when tryptophan is high?

• Hairpin in regions 2 & 3.

• Hairpin in regions 3 & 4.

• Repressor-operator complex.

• RNA polymerase-promoter complex.