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Β-Galactosidase Report

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Effects of Lactose on β-galactosidase Effect the Survival of Escherichia Coli
Trina Duncan
Introduction: Lac operon is a segment of DNA found in E. coli which is composed of two major DNA sequences: a promoter/operator sequence and structural genes (Kwiatkowski 2016). The promoter/operator sequence is basically the sequence of DNA that causes the process of transcription of the structural gene. Also when this sequence is ready to complete its job the structural genes will manufacture the β-galactosidase enzyme (KwiatkowskI 2016). ß-galactosidase converts lactose into glucose and galactose (Hampton). β-galactosidase was responsible for the breaking down of the disaccharide lactose into the two monosaccharides glucose and galactose (Kwiatkowski …show more content…
The results prove that lactose alone is an inducer and β-galactosidase is an inducible enzyme. Optimally, β-galactosidase is present in conditions where only lactose is present. Unexpected results were found with the tube labeled glucose + lactose showed no color change because CAP (Catabolite Activator Protein) cannot bind therefore transcription is turned off. According to Dr. Nan Hampton from the University of Texas, with no lactose present the repressor protein binds to the operator and the RNA polymerase is unable to initiate transcription of the lac mRNA. None of these three enzymes can be produced. With lactose present it binds to the binding site on the pressor protein and changes the affinity of the operator DNA. Now the RNA polymerase can initiate transcription of lac mRNA. Finally in conclusion to what Dr. Hampton recorded, he stated: that with glucose present, ATP is not converted to cAMP—which the cAMP comes from the conversion of ATP (Adenosine triphosphate).Thus, the CAP-cAMP complex cannot form and bind to the promotor. Resulting in very little lac mRNA

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