Gene Expression and Cell Specialization Quiz

The repressor can bind to DNA promoter regions on its own, but when ligands bind, it undergoes a conformational change and is no longer able to bind, causing gene transcription to occur.

Activators bind to DNA regulatory sequences and recruit RNA polymerase for transcription, but ligand binding can hinder their ability to bind and thereby block gene transcription.

An operon is a group of genes in prokaryotes that function as a single transcription unit, including an operator, promoter, and structural genes.

The lactose operon, for example, consists of three important genes: Lac Y, responsible for lactose uptake; Lac Z, responsible for lactose hydrolysis; and Lac A, of unknown function.

In the absence of lactose, the repressor binds to the operator region to inhibit transcription. When lactose is present, it acts as a ligand and causes a conformational change in the repressor, preventing it from binding to the operator and allowing transcription to occur.

The lac operon is regulated by both the repressor and the transcription activators cAMP receptor protein (CRP) and catabolite activator protein (CAP).

The presence of glucose, a preferred carbon source, keeps cAMP levels low, preventing CRP/CAP from binding and initiating transcription of the lac operon.

The trp operon, which encodes genes for tryptophan biosynthesis, is negatively regulated by the trp repressor, which binds to the operator sequence in the absence of tryptophan, preventing transcription.

In the presence of tryptophan, it acts as a co-repressor and binds to the trp repressor, causing it to bind to the operator and prevent RNA polymerase from binding, thereby blocking transcription.

Eukaryotes have more complex regulatory mechanisms involving multiple repressors and activators, as well as individual gene transcription rather than operons.

The repressor can bind to DNA promoter regions on its own, but when ligands bind, it undergoes a conformational change and is no longer able to bind, causing gene transcription to occur.

Activators bind to DNA regulatory sequences and recruit RNA polymerase for transcription, but ligand binding can hinder their ability to bind and thereby block gene transcription.

An operon is a group of genes in prokaryotes that function as a single transcription unit, including an operator, promoter, and structural genes.

The lactose operon, for example, consists of three important genes: Lac Y, responsible for lactose uptake; Lac Z, responsible for lactose hydrolysis; and Lac A, of unknown function.

In the absence of lactose, the repressor binds to the operator region to inhibit transcription. When lactose is present, it acts as a ligand and causes a conformational change in the repressor, preventing it from binding to the operator and allowing transcription to occur.

The lac operon is regulated by both the repressor and the transcription activators cAMP receptor protein (CRP) and catabolite activator protein (CAP).

The presence of glucose, a preferred carbon source, keeps cAMP levels low, preventing CRP/CAP from binding and initiating transcription of the lac operon.

The trp operon, which encodes genes for tryptophan biosynthesis, is negatively regulated by the trp repressor, which binds to the operator sequence in the absence of tryptophan, preventing transcription.

In the presence of tryptophan, it acts as a co-repressor and binds to the trp repressor, causing it to bind to the operator and prevent RNA polymerase from binding, thereby blocking transcription.

Eukaryotes have more complex regulatory mechanisms involving multiple repressors and activators, as well as individual gene transcription rather than operons.