Gene Regulation in Prokaryotes and Eukaryotes: Lac Operon, Transcription, and Post-Translational Control

What is gene regulation?

The process by which gene expression is controlled, ensuring not all genes are expressed all the time.

What are constitutive genes?

Genes that are always expressed regardless of the conditions.

What is the lac operon model?

A model of prokaryotic gene regulation found in E. coli that adjusts gene expression based on the presence of lactose.

What is an inducer in gene regulation?

A compound that stimulates gene expression by turning on the gene.

What is an inducible gene?

A gene that is activated by an inducer; its default state is off.

What components make up an operon?

A group of related genes and associated regulatory DNA sequences, found only in prokaryotes.

What is the role of the promoter in the lac operon?

The RNA polymerase binding site that is not transcribed.

What is the function of the operator in the lac operon?

An on/off switch sequence for gene expression.

How does negative regulation of the lac operon work?

It is governed by the presence or absence of lactose; no lactose means the operon is off due to the repressor binding to the operator.

What happens when lactose is present in the lac operon?

Lactose is converted to allolactose, which inactivates the repressor, allowing gene expression.

What is the result of transcription in the lac operon?

A single long mRNA is produced that is translated into three separate polypeptides.

What is positive regulation of the lac operon?

Regulation by an activator that binds DNA to stimulate transcription, increasing expression.

What is the role of catabolite activator protein (CAP) in the lac operon?

CAP increases the affinity of the lac promoter for RNA polymerase, enhancing transcription.

How does cAMP affect CAP activity?

Low glucose levels increase cAMP, which activates CAP to enhance RNA polymerase binding.

What is unique about eukaryotic gene regulation compared to prokaryotic?

Eukaryotic gene regulation is complex and occurs at multiple levels, including chromatin structure and transcription initiation.

How does chromatin structure affect gene expression?

Loosely packed DNA allows for gene activity, while densely packed DNA prevents expression.

What is the significance of transcription factors in eukaryotic gene regulation?

They are proteins that bind to DNA to promote or inhibit transcription initiation.

What is alternative splicing?

A process that allows different polypeptides to be produced from the same gene by including or excluding exons.

What is post-translational regulation?

The processing and modification of polypeptides to form the final protein, which must be correctly folded and chemically modified.

How does the length of the poly-A tail affect translation?

The length of the poly-A tail can influence the level of translation of the mRNA.