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Answer:
The LAC operon is a group of genes present in certain bacteria, like E. Coli that allow the cell to utilize sources of lactose as energy producers, instead of glucose. Normally, these bacterial cells prefer to use glucose because it is easier to handle, but in its absence, the LAC operon will be turned on in the presence and availabilty of lactose, especially when its polymer allalolactose is present, to initiate energy production.
This operon will encode for mRNA that will later on be translated into the necessary proteins that will ensure lactose management and digestion and aside from three different gene regions known as the lacZ, lacY and lacA, the operon also has a promoting signaling site called the promoter gene, and one that is called the repressor gene. Usually, the repressor gene region is the one that is active, as the E. Coli cell preferes to use glucose. But when this is not available, but lactose is, then the promoter will be turned on, while the repressor is removed, and coding will begin.
But in order for this to happen, two situations must be specifically met; otherwise the operon will not initate the process. First, glucose must be totally absent from the medium where the bacteria are. Second, lactose in the form of its polymer, allalactose, must also be present, because it will be allalactose, that will signal the cell to initiate the production of lactose enzymes and activate CAP (catabolite activator enzyme, which usually works when glucose is present, but that is also activated by allalolactose) to further activate the promoter gene in the operon. Then will transcription begin.
production will increase when B-gal is present on the media, while when removed, B-gal will not be produced
Further explanation
Lac operon is the operon needed in the transport and metabolism of lactose in E.coli and various other enteric bacteria. The lac operon consists of structural genes (lacZ, lacY, and lazZ), operator sites, and regulatory genes consisting of lacCRP, lacP, and lacO which are binding sites for cAMP protein receptors, RNA polymerases, and lactose repressors.
In the absence of lactose or other inducers, the repressor will still bind to lacO and prevent transcription because the binding of RNA polymerase is blocked at the lacP site, but the repressor concentration will decrease due to protein turnover or degradation and dilution by cell growth and division, so lacO will periodically released by the repressor, and RNA polymerase can bind to lacP and initiate transcription.
The production of B-galactosidase protein in comparison with the overall bacterial protein, it appears that production will increase when B-gal is present in the media, while when eliminated, B-gal will not be produced
In his experiments to detect the activity of lactose operons, light absorbance is usually used to measure the enzyme units formed, such as the addition of ortho-nitrophenol galactoside (ONPG) colorless compounds that function to measure the levels of β-galactosidase which will produce a yellow color over time and enzyme activity. ONPG will split into galactose and yellow nitrophenol, unlike IPTG, ONPG is not an inducer.
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Details
Class: College
Subject: Biology
Keywords: Lac operon, enzyme, nutrition
