What is the role of the lac operon promoter in prokaryotic gene expression?

There are two majors kinds of proteins that control prokaryotic transcription: repressors and activators. Repressors bind to an operator region to block the action of RNA polymerase. The lac operon is activated by the CAP (catabolite activator protein), which binds to the promoter to stabilize RNA polymerase binding.

What is the role of promoter in regulating gene expression in prokaryotes?

The promoter sequence is upstream of the transcriptional start site; each operon has a sequence within or near the promoter to which proteins (activators or repressors) can bind and regulate transcription. A DNA sequence called the operator sequence is encoded between the promoter region and the first trp coding gene.

Do prokaryotes genes have promoters?

In prokaryotes, the promoter consists of two short sequences at -10 and -35 positions upstream from the transcription start site. The sequence at -10 is called the Pribnow box, or the -10 element, and usually consists of the six nucleotides TATAAT.

How is gene regulated in prokaryotes?

Prokaryotic cells can only regulate gene expression by controlling the amount of transcription. It therefore became possible to control gene expression by regulating transcription in the nucleus, and also by controlling the RNA levels and protein translation present outside the nucleus.

How many promoters do prokaryotes have?

Prokaryotes only contain three different promoter elements: -10, -35 promoters, and upstream elements. Eukaryotes contain many different promoter elements: TATA box, initiator elements, downstream core promoter element, CAAT box, and the GC box to name a few.

How is gene expression different in prokaryotes and eukaryotes?

Prokaryotic gene expression (both transcription and translation) occurs within the cytoplasm of a cell due to the lack of a defined nucleus; thus, the DNA is freely located within the cytoplasm. Eukaryotic gene expression occurs in both the nucleus (transcription) and cytoplasm (translation).

What is function of promoter in operon?

A promoter is a type of protein that inactivates the expression of the lac operon genes by binding to the DNA of the lac operon . A promoter is a type of DNA sequence that activates the expression of the lactose genes by acting as an RNA polymerase binding site for the lac operon.

What is lac operon and how does it work?

1 Answer. The Lac Operon is an operon in E. coli that is required for the transportation and metabolism (“digestion”) of lactose. It (and various mutations) is often used in genetics courses to demonstrate gene regulation and expression. Explaining how it works is more easily done with pictures.

What regulates the lac operon?

The lac operon is regulated in “turn off” and “turn on” states based on the presence of glucose in the cell. The lac repressor is responsible for the ‘turn off’ mode of the lac operon while CAP is responsible for the ‘turn on’ mode of the lac operon.

What is the inducer in a lac operon?

The inducer in the lac operon is allolactose. If lactose is present in the medium, then a small amount of it will be converted to allolactose by a few molecules of β-galactosidase that are present in the cell. Allolactose binds to the repressor and decreases the repressor’s affinity for the operator site.

What is the role of the lac operon promoter in prokaryotic gene expression? There are two majors kinds of proteins that control prokaryotic transcription: repressors and activators. Repressors bind to an operator region to block the action of RNA polymerase. The lac operon is activated by the CAP (catabolite activator protein), which binds to the…