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

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.

i think the answer is b.