can anyone explain the functioning of lac operon in detail
Answers
Answer:
An operon is a functioning unit of genomic DNA that contains a group of genes controlled by a single promoter. ... The lac, or lactose, operon is found in E. coli and some other enteric bacteria. This operon contains genes coding for proteins in charge of transporting lactose into the cytosol and digesting it into glucose.
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Lac Operon
“Lac operon is an operon or a group of genes with a single promoter that encode genes for the transport and metabolism of lactose in E.coli and other bacteria.”
Lac Operon Concept
Gene regulation in prokaryotes can be explained with the help of the Lac Operon model. Here the alteration in physiological and environmental conditions can be observed leading to an alteration in expression in prokaryotes. It was observed by Jacob and Monod. The lac operon consists of:
Regulatory gene i – It codes for the repressor protein.
z gene – It codes for beta-galactosidase which catalyzes the hydrolysis of lactose into glucose and galactose.
y gene – It codes for permease which regulates the lactose permeability in the cell.
a gene – It codes for transacetylase which assists the enzyme beta-galactosidase.
Hence, all these genes help in lactose metabolism. In lac operon, lactose acts as an inducer. If lactose is provided in the medium for the bacteria, the regulatory gene is activated. The inducer will bind to the repressor protein and render it inactive which allows transcription of the operon. Thus, the lac operon is negatively regulated in this case.
Lac operon Notes
Lac operon contains genes involved in metabolism.
The genes are expressed only when lactose is present and glucose is absent.
The operon is turned on and off in response to the glucose and lactose levels: catabolite activator protein and lac repressor.
The lac repressor blocks the transcription of the operon. In the presence of lactose, it stops acting as a repressor.
catabolite activator protein activates the transcription of the operon, only when glucose levels are low.
