The lac operon contains three genes: lacz, lacy, and laca for β‑galactosidase, galactoside permease, and thiogalactoside transacetylase, respectively. the operon also contains a promoter site and an operator site. the regulatory gene includes the i gene for the lac repressor protein and a promoter for that gene. the lac operon undergoes negative regulation. in the normal condition, the lac repressor protein is active. allolactose, an isomer of lactose, is the signal molecule that binds to the lac repressor. determine which events will increase the concentration of lac gene products and which will decrease the concentration of lac gene products.

production will increase when B-gal is present on the media, while when removed, B-gal will not be produced

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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Lac operon

nutrition activity

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Class: College

Subject:  Biology

Keywords: Lac operon, enzyme, nutrition

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